Open-Air, Quench-Free Blade Coating of Photostable Triple Halide Perovskites for Tandems

Wide bandgap top cells for perovskite-silicon tandem devices are prone to light-induced halide segregation (LIHS) which leads to electronic and structural instability. We use additive engineering to assist with scalable open-air quench free fabrication of Cs0.22(FA0.8MA0.2)0.78Pb(I0.83Br0.14Cl0.03)3. Our work involves the polyvinylpyrrolidone (PVP) biopolymer additive which we believe passivates halide vacancies to fabricate a photostable film that has significantly improved optoelectronic and mechanical stability in response to illumination. We achieve smoother, more homogenous blade coated perovskite films with an improved photoluminescence response through controlling crystallization with PVP. These films show resilience to LIHS when exposed to a 50-sun equivalent laser irradiance in ambient. The in-situ stress response also shows a 50% reduction when cycled at 1-sun illumination in films with PVP compared to control films. This suggests improved stability to diurnal cycling and better mechanical integrity. We demonstrate LIHS results in a stress change and suggests that segregation can induce mechanical instability in the film.