Oxygen Degradation in Mesoporous Al<inf>2</inf>O<inf>3</inf>/CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3-</inf><inf>x</inf>Cl<inf>x</inf> Perovskite Solar Cells: Kinetics and Mechanisms

The rapid pace of development for hybrid perovskite photovoltaics has recently resulted in promising figures of merit being obtained with regard to device stability. Rather than relying upon expensive barrier materials, realizing market-competitive lifetimes is likely to require the development of intrinsically stable devices, and to this end accelerated aging tests can help identify degradation mechanisms that arise over the long term. Here, oxygen-induced degradation of archetypal perovskite solar cells under operation is observed, even in dry conditions. With prolonged aging, this process ultimately drives decomposition of the perovskite. It is deduced that this is related to charge build-up in the perovskite layer, and it is shown that by efficiently extracting charge this degradation can be mitigated. The results confirm the importance of high charge-extraction efficiency in maximizing the tolerance of perovskite solar cells to oxygen.This work was supported by SABIC and by the EPSRC, including by the Supergen Supersolar Consortium (EP/J017361/1) and the European Union Seventh Framework Program [FP7 2007-2003] under grant agreement 604032 of the MESO project. GE is supported by the EPSRC and Oxford Photovoltaics Ltd. through a Nanotechnology KTN CASE award. JW acknowledges the Swire Educational Trust for supporting his D.Phil. study at Oxford. We thank Sian Dutton (University of Cambridge) for access to XRD facilities and Felix Deschler (University of Cambridge) for helpful discussions.This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/aenm.20160001

Tillgängligt boende för äldre : Designförslag för anpassat småhus

De flesta äldre vill bo kvar i sina hem så länge de kan(Kärnekull 2011, 31). Men många tvingas till slut att flytta eftersom det blir omöjligt att bo kvar i hemmet. Den fysiska hemmiljön blir ofta ett hinder för de äldre att utföra vardagliga aktiviteter.(Abrahamsson och Nord 2012, 121) Syftet med studien är att visa om det är möjligt att anpassa ett bostadshus från 50-talet och göra det tillgängligt åt en äldre människa med funktionsnedsättning, som även ska fungera generellt för alla och utan att förstöra husets värden och karaktär. Syftet är också att undersöka och diskutera vilka för- och nackdelar de olika boendena för äldre har. Arbetet består av en litteraturstudie och ett designförslag. Litteraturmaterialet beskriver olika boende för äldre, hur boende anpassa till äldre och hur äldre personer egentligen vill bo. Objektet för designförslaget för en ombyggnation är ett 50-tals hus på Dahlsgatan i Gällivare. Designförslaget visar att det går att bygga om ett hus så att det är väl anpassat och tillgängligt för en äldre person och att huset efter ombyggnad även kan fungera generellt för alla utan att husets karaktär och värde har påverkats negativt

Oxygen degradation in mesoporous Al2O3/CH3NH3PbI3-xClx perovskite solar cells: kinetics and mechanisms

The rapid pace of development for hybrid perovskite photovoltaics has recently resulted in promising figures of merit being obtained with regard to device stability. Rather than relying upon expensive barrier materials, realizing market‐competitive lifetimes is likely to require the development of intrinsically stable devices, and to this end accelerated aging tests can help identify degradation mechanisms that arise over the long term. Here, oxygen‐induced degradation of archetypal perovskite solar cells under operation is observed, even in dry conditions. With prolonged aging, this process ultimately drives decomposition of the perovskite. It is deduced that this is related to charge build‐up in the perovskite layer, and it is shown that by efficiently extracting charge this degradation can be mitigated. The results confirm the importance of high charge‐extraction efficiency in maximizing the tolerance of perovskite solar cells to oxygen

Tailoring metal halide perovskites through metal substitution: Influence on photovoltaic and material properties

Mixed-metal compositional screening identifies Co2+ as capable of partial B-site substitution in CH3NH3PbI3, which supplies new dimensions of material tunability.</p

Determination of the exciton binding energy and effective masses for methylammonium and formamidinium lead tri-halide perovskite semiconductors

The family of organic–inorganic halide perovskite materials has generated tremendous interest in the field of photovoltaics due to their high power conversion efficiencies. There has been intensive development of cells based on the archetypal methylammonium (MA) and recently introduced formamidinium (FA) materials, however, there is still considerable controversy over their fundamental electronic properties. Two of the most important parameters are the binding energy of the exciton (R*) and its reduced effective mass μ. Here we present extensive magneto optical studies of Cl assisted grown MAPbI3 as well as MAPbBr3 and the FA based materials FAPbI3 and FAPbBr3. We fit the excitonic states as a hydrogenic atom in magnetic field and the Landau levels for free carriers to give R* and μ. The values of the exciton binding energy are in the range 14–25 meV in the low temperature phase and fall considerably at higher temperatures for the tri-iodides, consistent with free carrier behaviour in all devices made from these materials. Both R* and μ increase approximately proportionally to the band gap, and the mass values, 0.09–0.117m0, are consistent with a simple k.p perturbation approach to the band structure which can be generalized to predict values for the effective mass and binding energy for other members of this perovskite family of materials

Low-temperature processed electron collection layers of graphene/TiO <inf>2</inf> nanocomposites in thin film perovskite solar cells

The highest efficiencies in solution-processable perovskite-based solar cells have been achieved using an electron collection layer that requires sintering at 500 C. This is unfavorable for low-cost production, applications on plastic substrates, and multijunction device architectures. Here we report a low-cost, solution-based deposition procedure utilizing nanocomposites of graphene and TiO2 nanoparticles as the electron collection layers in meso-superstructured perovskite solar cells. The graphene nanoflakes provide superior charge-collection in the nanocomposites, enabling the entire device to be fabricated at temperatures no higher than 150 C. These solar cells show remarkable photovoltaic performance with a power conversion efficiency up to 15.6%. This work demonstrates that graphene/metal oxide nanocomposites have the potential to contribute significantly toward the development of low-cost solar cells. © 2013 American Chemical Society

Structured Organic-Inorganic Perovskite toward a Distributed Feedback Laser

A new strategy for structuring organic?inorganic perovskite materials for optoelectronic applications was studied. By conformally evaporating perovskite onto a nanoimprinted polymer resist, we were able to create a working perovskite distributed feedback (DFB) cavity and to tune the emission between 770 and 793 nm simply by varying the grating periodicity. DFB perovskite cavities have huge potential as inexpensive, mirror free, widely tuneable, single mode lasers that are easy to manufacture on a large scale. The DFB structure is highly versatile and can be optimized, for example, toward lower thresholds or different output energies. Broad tuneability may be achieved by utilizing the various closely related organic?inorganic perovskites and tailoring the cavity to the gain maximum of the unpatterned fi lm. With this approach, continuous tuning of the emission from 1.1 to 3.1 eV should be feasible which has relevance for telecommunication, medicine, and many other applications