Multifunctional Regulation of Chemical Bath Deposition Based SnO₂ for Efficient Perovskite Solar Cells

SnO₂ prepared by chemical bath deposition (CBD) is among the most promising electron transport layers for enabling high efficiency, large area perovskite solar cells (PSCs). However, the uneven surface coverage of SnO₂ and the presence of defects in the film and/or at the SnO₂/perovskite interface significantly affect the device performance. Herein, a multifunctional molecule of phosphorylcholine chloride (CP) is introduced to modulate the CBD growth of SnO₂ and suppress the generation of defects. The agglomeration of SnO₂ nanoparticles is hindered due to the electrostatic repulsion effect, leading to the formation of dense and conformal films with improved optical transmittance and electrical conductivity. Moreover, the defects both in SnO₂ and at the interface of SnO₂/perovskite are successfully passivated and the energy band structure is well regulated, contributing to the suppression of nonradiative recombination and the improvement of electron transport. As a result, a remarkably high power conversion efficiency (PCE) of 24.04% is attained for PSCs processed in air ambient. The unencapsulated devices exhibit improved long-term stability, maintaining over 80% of their initial PCE after storing in air ambient for 1500 h or under one-sun illumination for 600 h.