Dresden 2020 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 41: Perovskite and photovoltaics III (joint session HL/CPP)
HL 41.6: Talk
Wednesday, March 18, 2020, 11:15–11:30, POT 251
Tuning Perovskite Halide Content to Engineer Environmental Stability — •Katelyn P. Goetz1,2, Fabian Thome1,2, Paul Fassl1,2, Lukas M. Falk1,2, Vincent Lami1,2, Alexander D. Taylor1,2, Qingzhi An1,2, Fabian Paulus1,2, and Yana Vaynzof1,2 — 1IAPP, Technical University of Dresden, Germany — 2CFAED, Technical University of Dresden, Germany
The presence of surface defects in perovskite films has been linked to their stability; however, many questions remain regarding details of the degradation process. Here, we incrementally tune the iodine or bromide content in MAPbI3 or MAPbBr3 thin-films and examine the impact on optoelectronic properties. X-ray photoelectron spectroscopy is used to identify the density and type of surface defect. We examine the interaction of the defect with the environment by exposing the films to controlled levels of oxygen and humidity under light, and monitor changes to the films via photoluminescence (PL) spectroscopy. Here, we observe that, while halide-rich films exhibit lower PL quantum efficiency (PLQE) than halide-poor films, exposure to low levels of oxygen enhances the luminescence of all films. In solar cells, iodine-poor MAPbI3 samples show a tremendous drop in the short-circuit current after exposure to oxygen, while those with excess show no change. The MAPbBr3 solar cells show little dependence of the initial photovoltaic performance on the halide content, but upon exposure to air and light, bromide-deficient solar cells undergo a large Jsc boost, resulting in a near tripling of their initial PCE. These results highlight the strong role that chemical composition plays in stability.