Tandem på taket

Dette innlegget sto på trykk i Dagens Næringslivs teknologispalte 5. mai 2017. Det kan også leses på DN+, for dem som har det.

Skrevet av:

Trygve Mongstad, forsker ved Institutt for energiteknikk
Ørnulf Nordseth, forsker ved Institutt for energiteknikk

I dag relaterer vi ordet tandem til en lang og sjarmerende upraktisk sykkel – men i fremtiden kommer tandem til å være noe vi har på taket: Solceller.

Effektiviteten, eller virkningsgraden, til solceller er en av de mest avgjørende faktorene for konkurransedyktigheten til solenergi. De fleste av dagens solceller er laget av silisium. Silisiumbaserte solcellemoduler konverterer i gjennomsnitt 17 prosent av sollyset om til elektrisk strøm. De mest effektive modulene som er på markedet ligger på rundt 22 prosent, og det japanske selskapet Kaneka rapporterte å ha laget en silisium-solcelle med effektivitet på over 26,3 prosent i september i fjor.

Monokrystallinsk silisium er et fantastisk materiale, det kan lages med en renhet og en krystallinsk perfeksjon som ikke blir matchet av noe annet som vi mennesker kan lage i industriell skala. Likevel har materialet sine begrensinger. Den teoretiske maksimale effektiviteten til silisiumsolceller ligger på 29 prosent, så teknologien er nå nær grensen for hva som er mulig i industriell produksjon.

Men det finnes en mulighet for å lage enda mer effektive solceller – tandem. Med tandemsolceller er det mulig å gå forbi den teoretiske grensen, og det er derfor knyttet stadig større forventninger til denne teknologien. Rent teknisk består en tandemsolcelle av to eller flere individuelle solceller oppå hverandre. De er laget av forskjellige materialer, og hver solcelle tar opp forskjellige deler av fargespekteret i lyset. Ved i tillegg å konsentrere sollyset ved hjelp av en linse eller et speil er det demonstrert hele 46 prosent effektivitet. Man kan ikke sette opp linser og speil på bygninger fordi de trenger å snu seg etter sola, så denne teknologien er kun aktuell i bakkemonterte solparker i områder med mye direkte sollys.

Ved å kombinere silisium med et annet materiale kan det lages en tandemsolcelle som er relativt billig, effektiv og ikke trenger konsentrasjon av sollyset. På forskningskonferansen SiliconPV i Freiburg i Tyskland i april ble flere ulike løsninger for dette diskutert, og det ble vist at det er mulig å komme opp i over 30 prosent effektivitet med denne teknologien.

Utfordringen blir nå å utvikle materialer og en prosess som muliggjør høy effektivitet med tilstrekkelig lav kostnad. Én mulighet som har vært demonstrert er å kombinere silisium med perovskitt-solceller. Perovskitt-solceller er en lovende teknologi med potensiale for lave produksjonskostnader, som ikke er på markedet enda. Statoil gjorde i desember 2016 sin første investering i solcelleteknologi da de investerte i Oxford Photovoltaics, et selskap som utvikler nettopp denne teknologien. En annen mulighet er å bruke kobberoksid sammen med silisium, en løsning som nå forskes på av Institutt for energiteknikk i samarbeid med Universitetet i Oslo og samarbeidspartnere i Romania.

Bilde: I solcellelaboratoriet på IFE forsker vi på prosesser tilpasset silisiumbaserte tandemsolceller. Foto: IFE/Mick Tully, Image Commmunication. 

 

På kort sikt er det andre materialer enn perovskitt og kobberoksid som er mer realistiske for bruk i tandemsolceller. Forskere fra Fraunhofer-instituttet i Tyskland viste tidligere i år en effektivitet på 31,3 prosent i en silisium/galliumarsenid/galliumindiumfosfat-solcelle. Og det kan være snakk om ganske kort tid før denne teknologien er forventet på markedet. Ifølge det internasjonale teknologiveikartet for solceller (ITRPV, april 2017) forventes det at silisiumbaserte tandemsolceller settes i masseproduksjon fra rundt 2020.  

Selv om solceller nå er blitt en moden teknologi som leverer strøm til under markedspris i flere deler av verden, er det altså potensiale for forbedringer i effektiviteten som gir nesten dobbelt så mye strøm fra samme areal. Om ti år er derfor kanskje ikke tandem et ord vi forbinder med sykler, men derimot med takplatene og fasadene på de nyeste og mest energieffektive bygningene.

European projects relevant for silicon anodes in Li-ion batteries

A list of current European projects working on silicon-based anodes for Li-ion batteries. Compiled 24.02.2017. The source of this information is presentations given at the “European workshop on nanotechnologies and advanced materials for batteries” organized by Emiri, Umicore and CEA in Brussels 23-24 Feb 2017.

MARS-EV: Materials for Ageing Resistant lithium ion energy Storage for the Electric Vehicle

Coordinator: CIDETEC, Spain
Budget: 9 million EUR
Period: 2015-2017

The project develops all aspects of the Li-ion battery, intending to bring today's commercial Li-ion batteries one step further. High capacity anodes with a capacity of 1000 mAh/g over 1000 cycles is the goal. Silicon-carbon composites with a capacity of 600 mAh/g over 300 cycles have been demonstrated by the project partner Tel Aviv University, using multi-walled carbon nanotubes composites with silicon nanoparticles. At Imperial College London they have also developed a method for 3D imaging of silicon based electrodes using electron microscopy.

SPICY: Silicon and polyanionic chemistries and architectures of Li-ion cell for high energy battery

Coordinator: CEA, France

Budget: 7 million EUR

Period: 2015-2018

The project develops all aspects of the Li-ion battery, intending to bring today's commercial Li-ion batteries one step further. Several partners develop silicon-based anode materials: Laser-baser silicon-carbon core-shell materials by laser pyrolysis, nanostructured silicon and silicon-carbon alloys by plasma reactors. Very little information is available on the web page.

SINTBAT: Silicon based materials and new processing technologies for improved lithium-ion batteries

Coordinator: Varta Microbattery

Budget: 10 million EUR

Period: 2016-2020

This project promises us batteries with lower cost and life of 20-25 years. With 10.000 cycles as a goal, we are looking at batteries for electricity grid integration. The project aims to better understand the behaviour of silicon based anode by using advanced characterization methods as small angle neutron scattering and small and wide angle x-ray scattering. 

BACCARA: Battery and superCapacitor ChARActerization and testing

No web page.

Coordinator: CEA, France

Budget: 4 million EUR

Period: 2013-2016

Inspired by the problems of moving from half cell testing to full cells (realistic): Materials that deliver up to 300 cycles at very high capacity in half cells, break down after only about 10 cycles in full cells with realistic cathodes. The project has developed advanced characterization tools (NMR, FIB-TOF-SIMS, TEM-EELS, XPS, in-operando FTIR/Raman), and specialized tools as special cells and containers to avoid contamination of samples. The conclusion of the project regarding the failure of silicon materials is published in Nano Letters.

Figure: The failure mechanism of silicon anode materials according to the BACCARA project.

SIRIUS: Silicon RIUS (?)

No web page.

Coordinator: Nanomakers, France
Budget: 1.6 million EUR
Period: 2017-2019

This project aims to develop the second generation of silicon-carbon core-shell nanoparticles produced by laser pyrolysis by the French company Nanomakers. The project is supported by the EU through the industry organization EIT Rawmaterials. The project aims to increase the stability of silicon and to adapt the other components of the Li-ion battery to the silicon-based anode. Little information is available from Nanomakers about the project, but a recent paper describes a pilot reactor based on a similar principle of laser pyrolysis.

Silane gas safety

Silane accumulated below the bottle cap on silane bottles can cause a "popper" when removing the bottle cap. Always take care, use PPE including fire-proof gloves and closthes, and hearing protection when handling silane gas bottles. Photo: Dow Corning.

Our work on new ways to produce high-value silicon products at IFE is dependent on the gas monosilane. Monosilane, which we normally just call silane, is a gas consisting of molecules of one silicon atom and four hydrogen atoms. It is easy to purify and easily converts back to solid silicon, releasing its hydrogen atoms as gas. Because of this it is heavily used as an intermediate step in silicon purification, and in production of electronics components as e.g. flat screen TVs and advanced integrated circuits.

One of the main issues with silane is safety. The gas holds a lot of chemical energy and reacts violently with air if released through a leak, or if any other mistake is done. Therefore, focus on safe operation and the right maintenance procedures are crucial.

Some facts regarding silane safety:

• There have been several fatal silane incidents since the use of silane started in the 1960’s and 1970’s.
• Silane is pyrophoric: It can catch fire by itself when released to air (autoignition).
• Pyrophoric gases are somehow less dangerous than gases which are only flammable, because a fire generally gauses less damage than an explosion.
• Even though pyrophoric, silane will not always ignite when released. Especially when released at high pressure, it is often observed that there is no auto-ignition.
• If auto-ignition does not take place when released, often the gas actually auto-ignites when the flow from the high pressure reservoir is shut off.
• The most dangerous conditions occur under delayed ignition, especially if the gas release is confined or semi-confined, so that an explosive gas mixture can build up.
• If all precautions are taken, the chances of a serious incident are, luckily, minimal.
• It is not the amount of silane that determines the risk, any amount of silane represents a potential explosion and fire hazard.
• Another risk with silane, especially with using gases with two or more silicon atoms (disilane and higher order silanes) is the formation of “popping gels”. These can form in the exhaust handling systems, in the vacuum pumps or gas abatement systems, and are highly reactive solids that might “pop” or explode very violently upon any physical agitation.
• All handling of silane gas systems and silane based reactor systems should take place using proper personal protection equipment (PPE).

If you are interested in learning more about silane gas safety, do not hesitate to contact our group at IFE. I also recommend Eugene Ngai from Chemically Speaking, who has been working with silane safety and emergency response for over more than 40 years. See also EIGA's Code of Practice for Silane. 

Conferences concerning with silicon anodes in Li-ion batteries in 2017

Since I am working with the topic of usage of silicon in Li-ion batteries and I have not been able to find a good overview of the upcoming conferences within this topic, I make the list myself. This post will be continuously updated, and if you have further suggestion, please don't hesitate to leave a comment to this post and I will include it in the list. The conferences are listed in chronological order.

25-27 January 2017
Batterieforum Deutchland
Berlin, Germany
http://www.batterieforum-deutschland.de/
A session on silicon anodes on 26 January. NB: The conference language is German.

30 January - 2 February 2017
Advanced Automotive Battery Conference
Mainz, Germany
http://www.advancedautobat.com/europe/
A couple of silicon-relevant talks and probably posters on the morning of 31 January.
Abstract deadline (posters only): 9 December

14-16 February 2017
Next Generation Energy Storage
San Francisco, USA
http://www.knowledgefoundation.com/next-generation-energy-storage/
Probably less relevant for those of us who are working with materials.

20-23 March 2017
International Battery Seminar and Exibition
Ft. Lauderdale, USA
http://www.internationalbatteryseminar.com/
No specific mention of silicon in LIB in the program, but there will probably be a few posters at least.
Poster deadline: 17 February (talks by invitation only)

28-30 March 2017
Battery Day NRW 2017
Aachen, Germany
http://battery-power.eu/en/
German focus and to a certain extent in German language. About 10 posters on silicon materials in LIB announced on the web site.

22-26 May 2017
E-MRS Spring Meeting and Exhibit
http://www.european-mrs.com/meetings/2017-spring-meeting
No specific mention of silicon in LIB in the call for papers, but there are two relevant symposia which will probably extend over several days:
B: Advanced materials and systems for electrochemical energy storage
G: Materials for improving energy storage battery technologies
Abstract deadline: 18 January


This is not a complete list. Feel free to leave a comment below if you know of other relevant conferences.

Hvordan starte et forskningsprosjekt på fornybar energi i Norge?

Jeg ble "født" i en tøff verden som energiforsker. Da jeg var ferdig med doktorgraden min i 2012, var den norske solcelleindustrien ganske deprimert. For å bruke en meningsløs dobbelt-metafor; vi var på bunnen av en uendelig lang bølgedal og det var ikke noe lys i enden av tunnelen. Men, om ikke annet, så var det et fantastisk utgangspunkt for meg for å lære om hvordan man skaffer finansiering til forskningsprosjekter, og – ikke minst – om hva som faktisk er gode forskningsprosjekter. Og så gikk det faktisk ganske bra til slutt, i alle fall føles det nå som vi er ute av både bølgedalen og tunnelen.

Så, hva trengs for å få til et bra forskningsprosjekt? 

1. En god idé.
2. Riktige folk og riktig infrastruktur.
3. Penger.

Det er først når gode idéer møter gode folk med god infrastruktur og disse får penger til å forske at god forskning skjer. Det er ikke alltid så enkelt å få til.

Det som er ganske enkelt, er å komme på en god idé. Bare man vet hva som er problemet så kommer idéene ofte av seg selv. Vanligvis kommer en idé også sammen med noen folk. Men ikke alltid at de folkene som følger med idéen er nok, eller riktige folk. Et godt team til et forskningsprosjekt består vanligvis av forskere og brukere med ganske forskjellig bakgrunn, som kan bruke sin spisskompetanse sammen. Det oppfordres ofte til samarbeid mellom institutter (og land), noe som faktisk ofte ikke er så dumt. 

Det er når vi kommer til penger at det begynner å bli vanskelig. Her finnes det en skog av muligheter, men fruktene i denne skogen er ikke alltid så lette å få tak i, eller i det hele tatt å få øye på. 

La meg forholde meg til Forskningsrådet først og fremst: Forskningsrådet har en del ulike hoved-typer av forskningsprosjekter som er greie å forstå før vi går videre:

• IPN-prosjekt: Innovasjonsprosjekt i næringslivet. Dette er prosjekter der bedrifter vanligvis sitter i førersetet. Som navnet tilsier er dette en type prosjekt for å utvikle en spesiell innovasjon (oppfinnelse/produktutvikling/nye prosesser. Ofte vil det være med en eller flere forskningsinstitusjoner, som betyr universiteter eller forskningsinstitutter, men det er ikke nødvendig. Det er dog en fordel å involvere en forskningspartner som passer inn under punkt 2 på handlelisten over.
  Finansiering: Forskningsrådet støtter vanligvis bare med maksimalt 50% av kostnadene i denne typen forskningsprosjekt.
  Eksempler: Cenate (CENATE AS),  Cost-efficient silicon-carbon composites (Elkem)
• KPN-prosjekt: Kompetanseprosjekt for næringslivet. Denne typen prosjekt er mer grunnleggende, og handler om å bygge opp forskerkompetanse innen felter som er av interesse for norsk næringsliv. Det er alltid en forskningsinstitusjon (universitet, høyskole, forskningsinstitutt) som er hovedsøker, men det er vanligvis snakk om et samarbeid mellom 5-15 ulike forskningspartnere og bedrifter. KPN-prosjekter omfatter nesten alltid utdanning av én eller flere PhD-er.
  Finansiering: Bedriftene må bidra med minst 20% av totalbudsjettet, og de bør være genuint interessert i forskningen som blir gjort bør delta i forskningsarbeidet selv.
  Eksempler: Impurity control in silicon (IFE), HeatUp (SINTEF Energi).
• Forskerprosjekt. Denne typen prosjekt er vanligvis enda mer grunnleggende enn KPN-prosjekter. Imidlertid kan det dreie seg om en form for innovasjon, men i motsetning til IPN-prosjekter er det snakk om innovasjoner som har lang vei til kommersiell utnyttelse. Det vil typisk være forskningsinstitusjoner som oppdager noe interessant i sin forskning, eller ser en mulighet som deres kompetanse eller infrastruktur gir, som er nyvinnende og spennende men det er vanskelig å få bedrifter til å være med å støtte forskningen direkte. Det er kun forskningsinstitusjoner som kan søke om forskerprosjekter, men bedrifter kan være med som "interessenter". Prosjektene må være på topp internasjonalt nivå, og prosjektlederen må ha PhD innen et relevant emne. Det er ofte en komponent av utdanning av PhD-er, Postdocs og masterstudenter.
  Finansiering: Vanligvis 100% støttet av forskningsrådet.
  Eksempler: Siproco Fobeliba (IFE), 3D nanostructures for solar cells (SINTEF)
• FME: Forskningssenter for miljøvennlig energi. FME-sentre er store nasjonale samarbeid innen energiforskning, som ofte involverer flere forskningsinstitusjoner og flere titalls bedrifter. Det er lang tidshorisont (8 år) og totalbudsjettet kan være på flere hundre millioner kroner. Her snakker vi om flaggskip som skal organisere hele fagmiljøer i Norge og være hovedmotoren i fremdrift innen fagfeltet. Forskningsinstitusjoner er søkere, men det skal være tett samarbeid med bedrifter. På grunn av den lange tidshorisonten er FME-sentre til en viss grad organiske og kan forandre prioriteter under veis og kan også ta inn nye bedriftspartnere inn i samarbeidet. Det finnes per nå 11 FME-sentre, og i 2017 starter det opp 8 nye FME-sentre.
  Finansiering: Vanligvis 50% fra forskningsrådet, 25% fra forskningspartnerne og 25% fra bedriftene.
  Eksempler: NOWITECH (SINTEF), MoZEES (IFE).
• Andre prosjekttyper finnes også, men siden de er litt mindre vanlige går jeg ikke i detalj på dem, bla.: Unge forskertalenter, Nye konsepter, Idélab, SFI etc. Vanligvis vil disse ligne mye på en av de tre hovedkategoriene over her, men kan ha litt andre prosesser for evaluering. 

Dernest har Forskningsrådet en rekke ulike programmer som støtter ulike typer forskning. Programmene fungerer som en slags "underorganisasjoner" i Forskningsrådet og skal sørge for at det gjøres god forskning innen ulike temaer. Programmene som er særlig relevante for forskning på fornybar energi (sett fra mitt ståsted i alle fall), er:

• EnergiX: Dette er nok det viktigste programmet, som støtter forskning innen fornybar energi, effektiv energibruk, energisystem og energipolitikk. Det fungerer som et verktøy for regjeringen for å sørge for utvikling av ny energiteknologi, mest mulig utslippsfritt og helst med stort potensiale for å skape verdier og arbeidsplasser i fremtida. 
• BIA: Brukerstyrt innovasjonsarena støtter FoU-prosjekter som tar utgangspunkt i bedriftenes egne strategier. Her kan man nesten forske på hva som helst, så lenge forslaget kommer fra en bedrift og bedriften er villig til å betale rundt 60% av kostnadene selv.
• Nano2021: Dette programmet handler om å utvikle nanoteknologi, mikroteknologi og avanserte materialer. Det trenger ikke ha noe med energi å gjøre, men mye energiteknologi innvolverer jo denne typen materialer, så det er ofte mulig å søke støtte i dette programmet.
• Fripro: Dett er en åpen konkurransearena som favner alle fag. Dette er en slags prestisjetung konkurranse mellom alle forskere i Norge nesten uansett hva de jobber med. Det er muligheter for å få finansiert energiprosjekter her, men da bare for forskningsinstitusjoner og prosjektlederne må være lovende forskere som allerede har markert seg eller er tidlig i en lovende karrière. 
• Forny2021: Dette programmet skal jobbe for nyskaping ved forskningsinstitusjoner. Det vil kort sagt si "få ting ut av laben og ut i den virkelige verden". Her snakker vi forskning som er ment for å avklare sentrale spørsmål som er nødvendig å finne ut av for å få en idé kommersialisert. 
• Andre programmer: Forskningsrådet har ifølge sine websider 116 ulike programmer (på tide å rydde litt opp, kanskje?). De fem programmene jeg har valgt ut over her er de jeg selv har vært mest borti som energiforsker, men det finnes helt sikkert flere som kan være relevante.

Når vi nå vet hvilke typer prosjekter som finnes og hvilke programmer som finnes, er utfordringen å finne ut hvor forskningsprosjektet kan passe best mulig inn i denne tabellen:

Hvis man ikke har gjort dette før kan det nok være lurt å spørre seg litt rundt. Man kan ta kontakt med Forskningsrådet, spørre en kollega eller hvis man jobber i en bedrift vil det nok ofte lønne seg å ta kontakt med en forsker på et forskningsinstitutt eller et universitet som kan hjelpe til med søknadsprosessen. Forskere er ofte hjelpsomme og det kan til og med være hyggelig å snakke med dem, særlig hvis de får lov til å være med på forskningsprosjektet selv. 

Når det kommer til selve søknadsprosessen er det en egen historie. Det er ikke lett å skrive gode prosjektsøknader, i alle fall hvis man ikke har gjort det før. Det er ofte tøff konkurranse om midlene, selv om noen utlysninger er i stand til å finansiere opp til rundt 50% av søknadene de får inn. Uansett må søknaden være bra, og det er viktig å svare på alle spørsmål som kommer frem i utlysningen og søknadsmalen. Hver type forskningsprosjekt har sin egen mal, og programmene vektlegger ulike aspekter i forskningen. Forskere fra forskningsinstitusjoner ofte kunne hjelpe bedrifter med å få skrevet en god søknad, og det finnes også egne konsulentselskaper som har spesialisert seg på dette (f.eks. Nofas), men det kan være noe kostbart.

Det finnes også andre muligheter for støtte til energiforskning, her er noen linker:

• Miljøteknologiordningen i Innovasjon Norge
• Skattefunn
• Horisont 2020 - EU's store program for forskning, som fungerer omtrent som Forskningsrådet i Norge. Her er det enormt mange ulike muligheter, så det lønner seg å ta kontakt med noen som har jobbet med det før, eller sette av godt med tid til å få oversikt over mulighetene.

Inspirasjon: Forskningsrådet har i Prosjektbanken oversikt over alle pågående forskningsprosjekter støttet av Forskningsrådet. Her kan man for eksempel søke på Energi, og få opp alle prosjektene som har nevnt energi i sin beskrivelse. Eller alle prosjekter støttet av EnergiX-programmet.

Optical properties of amorphous and crystalline magnesium nickel hydride films

Magnesium nickel hydride (Mg-Ni-H) is a metal-hydride semiconductor which could find applications in e. g. solar cells. The material has earlier been investigated for the purpose of windows with controllable transparency, but the published literature describing the optical properties of the material is limited.

Thin-films of magnesium nickel hydride can be prepared in two forms; 1. an amorphous metal hydride resulting from hydrogenation of Mg-Ni films or in-situ deposition at room temperature and 2. a cubic crystalline structure resulting from hydrogentation of Mg-Ni films at high temperature (above 240 degrees C). The cubic crystalline structure resembles the well-known high-temperature (HT) structure of Mg2NiH4, but the structure is stable at lower temperatures also for the thin-film Mg-Ni-H.

In a recent paper* published in Thin Solid Films, we demonstrate that the cubic crystalline structure can be obtained by heating the amorphous films to approximately 250 degrees C. This is maybe not so surprising, since this is the temperature at which the HT structure of Mg2NiH4 normally forms. What is facinating, is that the crystallization treatment can be carried out in air, with lots of reactive oxygen present, and the films do not dehydrogenate or oxidize substantially. The films are therefore much more resistant than we believed in the start of our work.

The appearance of a gradient composition sample of amorphous (upper) and crystalline (lower) Mg-Ni-H films of ~500 nm thickness, deposited on glass. The transparent red and transparent yellow region in the amorphous and crystalline samples, respectively, correspond to the composition of Mg~2NiH~4. The samples are more Mg-rich on the left-hand side and more Ni-rich on the right-hand side. The difference in color demonstrate the change in band gap upon crystallization.

In the same paper we show the dielectric functions of both the amorphous and the crystalline films. The literature contains some scattered information on the optical properties of amorphous Mg-Ni-H, but the methods that have been used are not so strong and the reported dielectric functions are a little speculative. On the crystalline Mg-Ni-H, no values for the optical properties have been reported earlier.

The conclusion with respect to the band gap of these materials is 1.6 eV for amorphous Mg2NiH4 and 2.1 eV for cubic crystalline Mg2NiH4.

*Paper: The dielectric functions and optical band gaps of thin films of amorphous and cubic crystalline Mg~2NiH~4
Arxiv: Download article
Published in: Thin Solid Films
DOI: 10.1016/j.tsf.2012.07.044


For the convenience of future research projects working on Mg-Ni-H, I here give the calculated dielectric functions for amorphous and crystalline magnesium nickel hydride in tabulated format (download .xls sheet):

Thesis and defence of thesis

Last Friday I had the final defence of my thesis, at the Physics Department of the University of Oslo. I had a stressing couple of weeks before the defence, but when I was there it was actually quite a nice experience.

My two opponents were Aline Rougier from CNRS in France and Björgvin Hjörvarsson from Uppsala University, Sweden. Both of my opponents did an excellent job in pointing out the weaknesses and the strengths of my work. We also actually had a quite interesting discussion, especially concerning the photochromic effect in yttrium hydride films, but also on the origin and nature of oxygen in the samples.

Discussions with Björgvin Hjörvarsson and me about the origin of oxygen and chemical reactions in the deposition of thin-film metal hydrides.

To quickly summarize my work: I have been working with the deposition and characterization of thin films of metal hydrides, with the purpose of utilization in solar energy technology. Originally the focus was to develop metal hydride semiconductors for solar cell technology (see blogpost), and results with magnesium nickel hydride (Mg2NiH4) showed that this material had quite interesting properties for this purpose (see blogpost). Further, during my work I made the discovery of a strong photochromic effect in yttrium hydride films. This was the first ever demonstration of photochromism in a metal hydride at ambient conditions (see blogpost), and may thus have relevance for technological applications of photochromic materials.

The presentation I used for presenting my thesis in the public defence. Operate via the forward-backward controls in the bottom of the graphic.

My thesis, entiteled "Thin-film metal hydrides for solar energy applications" can be viewed and downloaded from academia.edu.

Workshop on metal hydride films for optoelectronic applications

Last week we had a workshop in our department, bringing together international experts within the field of metal hydrides, thin films and electrochromism in metal hydrides and oxides:

Participants at the workshop, from left: Dag Noreus (Stockholm University), Darius Milcius (LEI, Lithuania), Henrik Fahlquist (Stockholm University), Bernard Dam (TU Delft, The Netherlands), Smagul Karazhanov (IFE), Arve Holt (IFE), Kazuki Yoshimura (AIST, Japan), Sean Erik Foss (IFE), Aline Rougier (CNRS, France), Stefano Deledda (IFE), Trygve Mongstad (IFE), Yasusei Yamada (AIST, Japan), Jan Petter Mæhlen (IFE) and Volodomyr Yartys (IFE).

It was interesting to be able to discuss the opportunities with regards to these relatively new applications of metal hydride films. The two main points of interest was the recent advances in Mg-based metal films for electrochromic and gasochromic windows and the opportunities and questions that the recent discovery of photochromic effect in yttrium hydride films present.

Electrochromic oxides

Aline Rougier from CNRS in France set the background of the workshop with a survey of the status of electrochromism in metal oxide films. Metal oxides are more well-established than metal hydrides as chromogenic materials, and has been applied e. g. in automatic dimming of rear-view mirrors in cars, a technology commercialized by Gentex. Rougier has long experience with WO3 as an optically active element, and emphasized also that the synthesis of transparent conducting films is an integral part of the research challenges for electrochromics. The main challenge for implementation of electrochromics in smart window applications is the durability after thousands of switching cycles and the challenge of producing films that are uniform over a large area. Currently, a large research project under the 7th framework programme in the EU, Innoshade, is working on the development of oxides and organic materials for smart window applications.

Smart windows and hydrogen sensing

Kazuki Yoshimura and Yasusei Yamada from the AIST in Japan represent the currently most active research group on metal hydride films. Metal hydride films have the advantage that they become reflective rather than absorbing in the opaque state, which is favorable for windows that control the indoor solar irradiation and energy flow. In recent reports, the group of Yoshimura has demonstrated several impressive advances on gasochromic and electrochromic metal hydride-based devices. Among them are development of a "4th generation" of metal hydride films (Mg-alkaline earth) for switchable windows, durability tests and enhancement of cyclability from a few hundred cycles to several thousand and a full-scale experiment to test the energy performance of metal-hydride-based switchable mirrors with respect to static windows. The latter demonstrated 34% reduction on energy use for a room with electrochromic windows during a typical Japanese summer day. Several spin-off activities are on the way to be commercialized, as optical hydrogen sensors and a simple but innovative hydrogen detection sheet.

Phase transitions in Mg2HiH4

Dag Noreus from Stockholm university has long experience with Mg-based metal hydrides, working on structure determination of hydrides. In a collaboration with Darius Milcius from the Lithuanian Energy Institute, he has done work with films of Mg2NiH4, with the intention of demonstrating a pressure-sensitive metal-hydride switchable window. The idea was that the allotropes of Mg2NiH4 has very different optical properties, and experiments on powders have shown that phase transitions can be driven by applying mechanical pressure. However, no such response to mechanical pressure has yet been demonstrated for metal hydride films.

From switchable windows to nano-thermodynamics

Bernard Dam from TU Delft in the Netherlands has long experience with optical properties of thin-film metal hydrides, coming from the research group of Ronald Griessen who initiated this activity in 1996. Currently, there are several researchers in his group working on metal hydride films for optical hydrogen sensors. The activity directly related to switchable windows has been relatively low in the recent years. Work of Dam's group has further refined the thin-film metal hydride systems as a smart way to investigate nano-scale effects on the thermodynamics and stability of metal hydrides.

Photochromism in metal hydride films

As mentioned, the photochromic effect of yttrium hydride films was one of the main points of interest at the workshop. This effect was discovered in our group, reported in 2011. The effect is interesting on many levels: Firstly, it demonstratrates a new effect in metal hydrides which is of fundamental interest, something we should definitely learn more about. The properties of the effect suggests that the physical mechanism is different from what is found for photochromic metal oxides. Secondly, there are many reasons why this reaction is relevant for technological applications. It is probable that further research will lead to technological innovation. We hope to be able to further study this effect. Bernard Dam, who has been involved from the start of the work on photochromic yttrium hydride is also very eager to continue the studies.

Thin films of semiconducting magnesium nickel hydride

In a paper that became available online this week*, I describe our experience with making thin films of magnesium nickel hydride by using the method reactive sputtering. I am now getting closer to the objective of my thesis work (making "Scrap metal solar cells").

Magnesium nickel hydride (Mg2NiH4) is long known to be a semiconductor, but nobody has ever really tried to take advantage of that in technological applications. The band gap of this semiconductor is known to be a bit above 1.5 eV, which is quite close to the ideal band gap for a semiconductor in a solar cell.

One of the issues of why magnesium nickel hydride has never really been investigated for this purpose, is that most research on this material has been done on powders. It's quite intuitive that you cannot make a solar cell of a powder (although an innovative company actually is trying). So, it is crucial to be able to make the compound in a suitable form for solar cells; namely in the form of a film. That has been done earlier, but it is usually done by hydrogenation of a metallic magnesium nickel layer through a palladium cap. That type of film is, however, not so easy to work with, as the hydrogen will release from the film if you keep it in air, and you will be left with two layers of metals. Using reactive sputtering, on the other hand, we show that we can make films efficiently and that the films are quite easy to handle afterwards. This is really promising with regards to the actual use of this semiconductor in technology.

A Mg-Ni-H film with Al electrodes for electrical measurements.

* Paper: Magnesium nickel (hydride) thin films deposited by magnetron co-sputtering
Published in Journal of Alloys and Compounds
DOI: 10.1016/j.jallcom.2012.02.155


By the way, see also this nice article about our project that was recently published on the popular science news-site ScienceNordic: http://sciencenordic.com/new-material-solar-cells

Smart windows of yttrium hydride

Almost 40% of all energy consumed by humanity is used in cooling, heating, ventilating and lightning in buildings. Utilization of smart windows that automatically adjust the transmission and reflection of light and heat could drastically reduce this.

A few blogposts ago I wrote about our new synthesis method of making transparent yttrium hydride films. Yttrium and yttrium hydride films have earlier been used to make smart windows taking advantage of the hydrogen absorbtion in yttrium. It's a facinating reaction that was studied for many years, but due to a few drawbacks of this technology, it calmed off and never reached the market.

Now, just recently we made a discovery that might draw the attention to yttrium hydride based smart windows again. We found out that the transparent yttrium hydride films we had made had a very interesting reaction to light; they turned dark when they were illuminated! Under direct sunlight they gradually change colour, and the transparency is reduced by up to 50%. After the light exposure the material gradually turns back to its inital transparent state. This reaction is called photochromism, a very rare reaction which is observed very few existing materials.

The photochromic reaction in films of transparent yttrium hydride.

The reaction to light is indeed very fascinating. The video below gives an impression on how it works on a small sample deposited on glass, exposed to sunlight in our laboratory:

Imagine if a building in a hot and sunny area could reduce the energy consumption for cooling by up to 50% just by changing the windows! There are even more possible applications for this type of material, as sunglasses, displays, data storage etc. At the current stage we are working more on understanding what is really happening in this material and how to control the photochromic reaction.

Paper: "A new thin film photochromic material: Oxygen-containing yttrium hydride".
Published in: Solar energy materials and solar cells
DOI: 10.1016/j.solmat.2011.08.018

Solar cells with colors and high efficiency

Paper: Reduction of optical losses in colored solar cells with multilayer antireflection coatings
By: Josefine Selj, T.T. Mongstad, R. Søndenå and E.S. Marstein
Published in Solar Energy Materials and Solar Cells (2011)

You may have noticed that solar cells are normally dark blue or almost black in color. The reason for this is that you want to take as much as possible out of the light that hits the solar cell into the cell to generate electricity.

It is obviously best to have a totally black panel, but you can not just paint the panel black, because in that case you will not let any of the light into the cell, all of the light will be absorbed in the paint. The solution is to make an anti-reflective coating, a very thin layer of a transparent medium on top of the solar cell, that traps the light in the cell because of what we call destructive interference. The thickness of these layers are about 70 nm in normal solar cells, or about 1000 times thinner than a human hair. That thickness correponds to 1/4 of a wavelength of visible light, which means that the reflected light from the lower surface gets canceled out by the incoming light when it meets the surface and "wants to get back out". This is a well-known strategy to trap the light, which is applied in all solar cell concepts.

An anti-reflection coating made up by a single thin film reduces the reflection from a solar cell from around 30% to below 10%, as can be seen in the graph in Figure 1. If you are in doubt what the "wavelength of the light" means, it is a complicated way to say "color of the light" (See Color on Wikipedia).

Figure 1 - Reflection spectra as a function of the wavelength of the light, from a silicon wafer with and without single antireflection coating. 

This is all old news, and it is also old news that the color of the solar cell depends on the thickness of the anti-reflection coating (See graphic here). So, one can make solar cell with other colors also. That would of course be nice with artictecture in mind, that you can choose which color you want to have on your cells. The problem about that, is that as you change the thickness of the film, and thereby the color, you get quite much reflected light from the cell, so you loose a lot of efficiency. 

That's why we in a project we started approximately one year ago, decided to look at colored solar cells, and try to find a way to get nice colors without loosing so much light. We found that by using several layers of different very thin films we could both control the color of the solar cell, and keep the efficiency reasonably high. My colleague Josefine is an expert on porous silicon, which can be used to make very good anti-reflection coatings by making very many very thin layers with different optical properties, and she found that one could use porous silicon to make colored anti-reflection coatings without loosing more than 1% (absolute) of the efficiency (Figure 2). Also the more traditional coating silicon nitride in combination with silicon oxide turned out to give strong colors without loosing much of the efficiency (Figure 3).

Figure 2 - Colored reflection from spots on a silicon wafer on which a porous silicon anti-reflection coating has been applied.

Figure 3 - Green, red and blue color from a 3-layer stack of silicon nitride and silicon oxide. These layers are optimized to get as much efficiency as possible in combination with these nice colors.

In this work, we did not actually make any solar cells, we just made the antireflection coatings and calculated what the efficiency would be according to optical measurements on the samples. Indeed, colored solar cells are available on the market (see e. g. Lof solar), and I think we will see more of this in the future as building-integrated photovoltaics become more and more common.

Read the paper.

Paper: Transparent yttrium hydride films prepared by reactive sputtering

Last week the first scientific paper where I am the first author became available on the internet. That is of course a grand step for me on the way to obtaining my PhD degree.

It was a bit more than one year ago that I had just started working with a new material in my sputtering machine. I had an idea that I could make some nanometer-thick layers of a semiconducting material called yttrium hydride by putting layer by layer of yttrium atoms on a surface, while the whole process was going on under the presence of hydrogen gas. Yttrium is a somewhat rare metal (not so rare as to be extremely expensive), and by reacting with hydrogen it transforms into yttrium hydride. This yttrium hydride can appear metallic, black or yellow-transparent, depending on the amount of hydrogen absorbed. The transparent state was what interested me as a potential material for solar cells.

Thin layers of yttrium hydride had already been made by others, and was first reported in 1996 by a group in the Netherlands. However, as it is difficult to make yttrium take up hydrogen directly, the films were made by putting a thin layer of palladium on top of the yttrium film, and then exposing them to hydrogen gas. The palladium is helping to take up the hydrogen, but there are some problems. Firstly, it is an extremely expensive material, which has a similar price to gold. Secondly, in addition to help to take up hydrogen, it also helps the hydrogen to escape, so if you take the yttrium-palladium sample out of the hydrogen gas, it does not remain in the same state. These were my reasons to try this new method reactive sputtering, which had not been utilized before for this exact material.

Since this was a new method for this material, my expectations were not so high. First, I started just laying layers of yttrium atoms on some glass, and got some metallic-looking films that had the expected properties for yttrium metal films. Then I put some hydrogen on, and I was content to observe that I obtained films that were darker, similar to the black state of yttrium hydride. Then, increasing the hydrogen pressure a little bit more, I got a film with the transparent state of yttrium hydride! I was very happy to have been able to make this kind of material by a completely new method, and surprised by the facility with which I had done it.

Figure 1 - I was very happy to see how easy it was to form transparent, black and metallic (left to right on the photo), just by adjusting the hydrogen pressure in my process.

The last year, I have spent working on these samples. Unfortunately I have not been able to make any solar cells of this material, but I have discovered a lot of other interesting things. Some of them, like the finding that these films have a cubic crystal structure as opposed to hexagonal in other findings for the transparent yttrium hydride material, can be read about in the present paper. And for the people that are not metal hydride geeks, I can already tell you that some much more interesting reports will come out soon, subject of one or more papers I hope to wright in the near future.

Published in Journal of Alloys and Compounds, DOI: 10.1016/j.jallcom.2010.12.032

Get the paper (open access PDF).

Scrap metal solar cell

T. Mongstad, S. Zh. Karazhanov, D. M. O. Heggø

A quest for new materials that can be suitable for solar cells has been going on over the last 50 years. Some good candidates have been found and even successfully commercialized, but the rarity of elements that are essential for these technologies is eventually expected to be their Achilles heel. In order to make a serious contribution to the transition from fossil fuels to renewables, a solar cell technology has to be based on abundant elements. IFE is now investigating a new class of materials, which could result in a highly efficient solar cells made of scrap metal!

Limitations for thin film photovoltaics

Currently the most successful alternatives to crystalline silicon (Si) are copper indium gallium selenide (CIGS) and cadmium telluride (CdTe). The last 10-15 years has brought these so-called thin film solar cells from the research labs to the factories. You can now buy both CIGS and CdTe solar panels with efficiencies that are approaching that of crystalline silicon (Si) solar cells, at a lower cost than for Si cells. The efficiencies are still increasing, which is promising. However, there is a show-stopper. An important constituent in the CIGS cells is indium, which is a rare and expensive element. For CdTe cells, which at present is the cheapest solar technology measured in cost per watt, the tellurium (Te) gives a similar problem. The limited abundance of these elements puts a roof on the production, and these technologies may run into difficulties in as little as 10 years [1].

Expensive 3^rd generation cells

Crystalline and multicrystalline silicon solar cells are still dominating the market. The efficiency-to-cost ratio is continuously getting better, but we are bound to reach a limit. The theoretical limit for silicon solar cell efficiency is around 30%, and it is highly unlikely that it goes beyond 20% for reasonably priced silicon solar cells. In spite of this limitation, silicon cells will still be around for a long time. But at some point we will move into more complex technologies, and one solution is tandem solar cells. Tandem solar cells selectively absorb light in different materials to get the most out of every photon. This technology has actually proved to give more that 40% efficiency in laboratory cells, but unfortunately this has only been achieved with the use of extremely expensive materials.

Metal + hydrogen = metal hydride

Metal hydrides can be the solution. By adding hydrogen to different metals we can get materials that are semiconducting, which means that they can be capable of generating electricity in a solar cell device [2]. Semiconducting materials based on abundant metals in combination with hydrogen might be the solution to the problem with rare and expensive elements. And by choosing different metals and alloys, we also can easily make materials that absorb different parts of the sunlight.

Using metal hydrides we might be able to make a highly efficient tandem solar cell out of “scrap” metal. IFE has ongoing experimental work on making thin films of semiconducting metal hydride films for photovoltaics, and we have so far showed results with magnesium [3] and yttrium [4] hydrides.

Figure 1: The author with a transparent semiconducting yttrium hydride sample (left) and a metallic yttrium sample (right). The only difference between these samples is the content of hydrogen!

Further reading:

[1]       B.A. Andersson, “Materials Availability for Large-scale Thin-film Photovoltaics,” Progress in Photovoltaics: Research and Applications, vol. 8, 2000, pp. 61-76.

[2]       S.Z. Karazhanov et al., “Hydrides as materials for semiconductor electronics,” Philosophical Magazine, vol. 88, 2008, pp. 2461-2476.

[3]       C. Platzer-Björkman et al., “Reactive sputtering of magnesium hydride thin films for photovoltaic applications,” Materials Research Society Fall Meeting, Boston: 2009.

[4]       T. Mongstad et al., “Transparent yttrium hydride thin films prepared by reactive sputtering”, Journal of Alloys and Compounds, (in preparation) 

Papers and journals

I'm an experimental scientist. I spend much time in the laboratory, but still I think I spend most of my time reading scientific papers. Scientific papers are texts written by scientists, for scientists. People not working in science would generally not understand anything of such a text, and it may even prove difficult for a scientist to understand a paper about a subject that she is not working with especifically. I mean, I'm a physisist, and I would of course not understand so much a scientific paper about lung cancer, but also papers about different areas of physics can be super-greek to me.

Being a scientist is revolving around these papers, and a scientist is generally evaluated on the basis on the papers she has written. Applying for a future job, she needs to refer to good papers in good journals with a lot of citations. In some countries you will get bonuses and raises as a scientist based on the papers you have written. Good papers and citations will also make it easier for you to establish new research projects and apply for official funding.

As a PhD candidate, the main objective is actually to write these papers. I need to write about 4-6 of them for my PhD degree to be approved. A paper can be anything from three to twenty pages. It sounds easy, but it's a real pain. For writing a paper of three pages I have to spend half a year in the laboratory pulling out my hair and another half in the office reading the thousands of pages other scientists have written before me about similar subjects.

Scientific journals are really not journals any more. I have not seen a journal since I started working on my PhD about a year ago. Well, many people have heard about Science and Nature, that are scientific journals that you might actually find on the shelf in the library. However, most researchers just use the on-line versions, which are databases of papers. If you know the author, the journal and the year a paper was published, you can find it.

But these journals are actually not so easy to get to. People outside universities that try to find a scientific paper, might find it, but would normally have to pay 50 dollars or so for downloading the document. If you are in a university you can download it for free, but the universities pay extremely large amounts of money to have this access. Who gets the money? Certainly not the actual scientists. I will not get any money publishing a paper, and I would actually have to pay for publishing it if I send a paper with color photographs.

And there is also the choice about the journal which you want to publish in. The journals are rated, they have what is called impact factor, which says something about how many people read the papers in this journal. Here is a list of impact factors for journals that are relevant for me:

• Nature: 34.5
• Science: 29.7
• Physical Review Letters: 7.8
• Solar Energy Materials and Solar Cells: 3.9
• Applied Physics Letters: 3.6
• Physical Review B: 3.2
• Europhysics Letters: 2.9
• Journal of Alloys and Compounds: 2.1
• Journal of Applied Physics: 2.1

Well, highest is of course best and everybody wants to publish in Nature. But that's nearly impossible for a normal scientist as me. When you send a paper to a journal, the editor will take a look at it, and if it's not a total crap she will send it to a set of reviewers, which are experienced scientists within the same field. They will evaluate if it's a good enough paper for publishing, and then probably send you back some comments about things you should change or clarify. 

Scientific papers are normally written by 3-10 co-authors. That means in practice that one PhD student writes the paper, and another five people just want to put their names on the paper for their own convenience. Well, it's not so bad, having experienced scientists reading through your paper and keeping themselves informed can be to great help to a PhD student.

So, there is a lot of things to keep track of. I just submitted my first paper, I sent it to Journal of Alloys and Compounds, which as you see is on the bottom of the list of journals. I have to start somewhere!

Life in a cleanroom

A cleanroom is a room within the laboratory with extra low concentration of dust and contaminating particles. To be in the cleanroom I have to dress up in a funny yellow suit to protect the environment from my dusty body. I can not bring normal paper inside, and I can not use my cellphone without a special bag to put it in, for example. Some times I work the whole day in here, but going in and out, dressing up in the funny yellow suit 15 times a day just to sit in front of my piece of lab equipment for hours without even beeing able to bring a book or a printed paper to read. But it gives me some time to think about stuff, it gives me a certain distance to the rest of the world. There is a window here, where I can see the rest of the laboratory from, I can see my colleagues running around in their white lab coats while I stand there in my funny yellow suit waiting for my laboratory processes to finish.

Financial crisis in photovolatics

Growth in 2008, growth in 2009, growth in 2010. I am not a financial analyst, but it seems to me that we are on the right way. Recharge reports that a 40% growth is expected in 2010, which is more or less the mean value for growth in the number of installed solar cells per year over the last ten years. If this growth continues for the next 20 years, the annual production in 2030 of solar energy will be of more than 40.000 TWh. That is approximately 1/3 of the total energy consumption per year in the world today!

Spinning electrons

I have now been in Grenoble in France for a couple of weeks, where I am doing a course on what experiments can be done with synchrotron x-rays and neutrons. Here in Grenoble, one of the most powerful synchrotrons in the world is situated, which I guess is the reason for the course taking place here. We are a group of 75 students on the course, most of us are PhD candidates, but there are also some senior scientists. The course is called HERCULES, and it has been on each year for 20 years now. That means that quite a bit of the research community working with synchrotron and neutron radiation has been through this course, and they have a pretty good line-up of lectureres.

Anyway, what's a synchrotron? Well, it's a big ring where electrons run around at a speed close to the speed of light. They are kept going around in the circle by magnetic fields that are guiding them around. When these electrons are pulled around by the magnetic field, they start emitting very high energetic radiation in the same direction as they are propagating. This radiation is mainly consisting of x-rays, which can be pretty useful for many things. The main thing about x-rays, as you probably know already, is that they go through things that normal light does not go through. They are also smaller (have shorter wavelength) than light, so they can see smaller things. And last but not least, if they propagate through a crystal, the atoms in the crystal can spread the x-rays into a special pattern that gives a lot of information about the crystallic structure. That's what's important to me, and many other researchers. A lot of things are crystalline, and certainly most semiconducturs, which is what we are making solar cells of. But you can discover crystalline structures even in chocolate, as some of the participants in the course have been able to see in their practicals.

Neutrons techniques is the other subject of the course. The neutrons can do similar things as the x-rays. Although neutrons constitute about half of the matter on earth, they are not so easy to get out from the atoms. You actually need a huge thing to kick the neutrons out, as for example a nuclear reactor. The fission of uranium gives neutrons flying out in every direction, which in energy reactors could be considered a problem. However, the neutrons has the property that they penetrate through things that not even x-rays would consider possible, so they can be quite
useful for structural analysis.

Here's a photo of the synchrotron ring and the reactor here in Grenoble, from a photo I took on my mountain hike this Saturday:

Metal hydride switchable windows and mirrors

The metal hydrides I am trying to make solar cells of, can also be used to make switchable windows. When hydrogen is added to a thin film of some of the metal hydrides, an abrupt transition from metallic or black to transparent can be observed. It has not yet reached any high grade of commercialization, but switchable windows are believed to become tomorrow's curtains for offices and lazy people wanting to shut the curtains with an application on their iPad.

Bad results make nice photos

I am making thin films of transparent metal hydrides, using a method called reactive sputtering. The samples I prepare react strongly with oxygen after the preparation, which I really do not want them to do. To avoid the sample to take up oxygen from air, I therefore cover them with metal before exposing them to air. But it it is not always successful. Some times the metal capping is too thin, and the oxygen goes through the film, creating tiny cracks and craters. The images above are microscope images of the cracks and craters, taken with an optical microscope trough the transparent films.

The colours are created by light interference in the film, the same effect that creates rainbow-like colours when a thin cap of oil is lying on top of water or wet asphalt, which you probably all have seen.

Review: Sony Ebook Reader for research (and little things)

For quite some years I have anxiously been expecting the emerging of the digital book. I have been following the development and the releases of the Kindle from Amazon, as you all might have heard of. But I was actually never really attracted to the Kindle. It seems to proprietary for my taste, and it has a lot of things I really do not need.

So, when I was in the US in December, I went to a Sony store just to see what was up, and there was the Sony Reader Touch Edition PRS-600. I was immediately attracted to the fancy little gadget, and after a day of tough consideration I bought it as a birthday present for myself.

The justification I presented for myself, was that this was something I needed for my research. As a researcher, I have hundreds of journal papers to read, and they are all in my computer in PDF format. The ebook reader would make me able to take advantage of the time I spend on the bus going to and from work, and it would make me able to carry an incredible heap of documents where ever I go. Perfect!

And what do I think? The ebook reader has been accompanying me now for almost two months, and I am really very happy about it. It reads the PDF documents very nicely, and the e-paper in combination with the opportunity to take notes directly on the touch-screen make it very much similar the real paper experience.

Getting away from the computer can also be a great pleasure at times. I can have real trouble in concentrating when trying to read something complicated in the computer screen, as I have gotten so used to the restless zapping between documents and endless information search on the internet. Printing the important documents was always necessary when it was something important, but this is no longer the case. I save paper, and my desk does no longer look like a big mess.

But real paper is still there. I still read real books when on the bus, and I still print some documents. The reader is a small device, which can of course be convenient for carrying it around, but for reading comfortably it would have been better having a display of at least twice the size of this one. The contrast of the screen is not extremely good, so it requires quite good light to read well. Another thing that should be commented is that it does react a little slow, especially when reading scanned PDF files and taking notes in them. For scrolling through large documents this is definitely not the solution.

But after all, it because of all the little things I have really started to love my ebook. Just slipping the SD-card into my computer makes it so simple to put documents onto it, and it can be used to carry anything from cooking receipts to bus timetables. The opportunity to take notes is also really handy because I carry it almost anywhere, and I do not have to worry about where I left that damn piece of paper where I put down the reservation number of whatever, you know?

I recommend utilizing an ebook for research and all the other little things. But if you are in doubt, you could always wait one more year for the larger versions to get on the market.