High Efficiency Quasi-2D/3D Pb–Ba Perovskite Solar Cells via Phenethylammonium Chloride Addition

The existence of toxic Pb in perovskite solar cells may hinder the pace of commercialization. Based on the previous work, Ba²⁺ is most suitable for partially replacing Pb²⁺ among alkaline-earth metal cations. However, a high substitution ratio may lead to poor film coverage. A detailed study of the effects on film formation with phenethylammonium chloride (PEACl) additive for large n (n > 40) quasi-2D/3D mixed-cation Pb–Ba perovskite (i.e. PEA_xMA_0.4−xFA_0.6Pb_0.9Ba_0.1I_yCl_3−y) is presented. The perovskite layer with defects passivation exhibits efficient charge-carrier transport, suppression of trap-assisted recombination, and improved electron extraction capability. The mapping distribution of surface potentials is quantified by photo-assisted Kelvin probe force microscopy to verify the carrier generation. Consequently, the power conversion efficiency (PCE) of the PEA_xMA_0.4−xFA_0.6Pb_0.9Ba_0.1I_yCl_3−y perovskite solar cell is enhanced significantly from an averaged PCE of 15.0% of the pristine active layer to 18.1% and the champion PCE can achieve 19.1%. The corresponding device shows outstanding long-term stability in air, retaining 90% of its initial PCE for more than 700 h. Herein, a promising strategy to passivate defects and improve the perovskite film quality for superior optoelectronic properties is provided.