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While the susceptibility of CH 3 NH 3 PbI 3 to water is well-documented, the influence of water on device performance is not well-understood. Herein, we use infrared spectroscopy to show that water infiltration into CH 3 NH 3 PbI 3 occurs much faster and at a humidity much lower than previously thought. We propose a molecular model in which water molecules have a strong effect on the hydrogen bonding between the methylammonium cations and the Pb−I cage. Furthermore, the exposure of CH 3 NH 3 PbI 3 to the ambient environment increases the photocurrent of films in lateral devices by more than 1 order of magnitude. The observed slow component in the photocurrent buildup indicates that the effect is associated with enhanced proton conduction when light is combined with water and oxygen exposure.

Efficient solar energy conversion with CuInS2 thin films is reported. The copper-rich p-type absorber is prepared by thermal coevaporation. A copper to indium ratio between 1.0 and 1.8 can be tolerated with small (≤10%) solar-to-electrical conversion losses. Copper excess phases (CuS) are removed chemically. The cell structure glass/Mo/p-CuInS2/n-CdS/n+-ZnO/Al delivers 10.2% at simulated AM 1.5 conditions. The device properties are discussed based on its energy band diagram.

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Perovskite solar cells based on (CH3NH3)Pb(I,Cl)3 have recently demonstrated rapidly increasing cell efficiencies. Here, we show progress identifying phases present during the growth of (CH3NH3)Pb(I,Cl)3 perovskite thin films with the vacuum-based coevaporation approach using two sources under varying deposition conditions. With in situ X-ray diffraction, crystalline phases can be identified and monitored in real time. For different (CH3NH3)I-to-PbCl2 flux ratios, two distinct (CH3NH3)Pb(IxCl(1-x))3 phases with high (x > 0.95) and with lower (x < 0.5) iodine content as well as a broad miscibility gap in-between were found. During post deposition annealing we observe recrystallization and preferential orientation effects and finally the decomposition of the perovskite film to PbI2 at temperatures above 200 °C.