Impact of Antisolvent and Gas Quenching on Wrinkling in Cs _0.15 FA _0.85 Pb(I _0.6 Br _0.4 ) ₃ Perovskite Films

The surface topography of the lead halide perovskite layer is a crucial aspect that influences the performance of perovskite solar cells (PSCs). In this work, two different quenching approaches for the crystallization of Cs_0.15FA_0.85Pb(I_0.6Br_0.4)₃ perovskite films are investigated: antisolvent quenching and gas quenching. Both methods, aimed at removing the solvent of the precursor solution and initiating the perovskite nucleation, differ mechanistically and result in different rates of crystallization, which cause surface topographical irregularities, in the form of elongated and elevated structures on the films, termed "wrinkles". This study shows that antisolvent-quenched perovskite films exhibit a higher density of wrinkles than the gas-quenched counterparts. Pinholes were found along the wrinkles; thus, a higher density of wrinkles leads to more pinholes and to more defective surface topography. The wrinkles also make the surface rougher, hindering homogeneous contact with the adjacent passivation layer and reducing the overall performance of the solar cells. By comparing the two different quenching methods, we obtained insight into the formation of the wrinkles and their effects on the optoelectronic properties of the perovskite films. We identify the gas quenching method as a way to reduce the wrinkle density to achieve better photovoltaic performance in comparison with the antisolvent method.