In Situ and Operando Scattering Studies on Perovskite Solar Cells

The first application of hybrid organo-metal halide perovskites as sensitizer in hybrid solar cells marked the cornerstone for what has now become a broad field of extensive research. After overcoming initial challenges, power conversion efficiencies (PCE) of hybrid perovskite photovoltaics strongly increased to above the 25 % mark and now outperform many conventional inorganic thin film technologies for solar cell fabrication. The easy and versatile processing towards an improved stability and reproducibility further increases the massive interest in this type of material. The abundance of precursor materials in combination with the wet chemical processing are rendering hybrid organo-metal halide perovskites as candidates for a low-cost, mass-production photovoltaic technology. However, still the limited reproducibility of the device fabrication and the limited device stability impose challenges to bringing perovskite solar cells to real world applications.<br/>With advanced in-situ x-ray and neutron scattering methods, the perovskite film formation is followed with a very high temporal and spatial resolution. In particular, with multi-modal grazing incidence small- and wide-angle X-ray scattering (GISAXS and GIWAXS) studies, we gain information on the kinetics of inner structures forming during processing. From these data, models about the morphology evolution are extracted and these models guide the fundamental understanding to increase reproducibility in the solar cell fabrication. [1]<br/>Extensive studies have focused on improving the operational stability of perovskite solar cells, but few have surveyed the fundamental degradation mechanisms. One aspect overlooked in earlier works is the effect of the atmosphere on device performance during operation. Here, we investigate the degradation mechanisms of perovskite solar cells operated under vacuum and under a nitrogen atmosphere using synchrotron radiation-based operando GISAXS and GIWAXS. [2]<br/><br/>[1] Nat. Commun. <b>12</b>, 5624 (2021)<br/>[2] Nature Energy <b>6</b>, 977-986 (2021)