Enhancing Device Performance in Quasi-2D Perovskite ((BA)₂(MA)₃Pb₄I₁₃) Solar Cells Using PbCl₂ Additives

Quasi-2D Ruddlesden–Popper perovskites exhibit excellent photostability/environmental stability. However, the main drawback is their relatively low photovoltaic properties compared with three-dimensional perovskites. Herein, we demonstrated that chlorine-based additives via adjusting the proportion of PbI2 and PbCl2 in the precursor (BA)2(MA)3Pb4I13 (n = 4) solutions show an optimized device performance of over 15%, and the devices exhibit much improved humidity stability. Upon PbCl2 addition, the quasi-2D perovskites have larger and more compact grains, which result in high quality of films. The photoluminescence gives rise to a much prolonged lifetime under the PbCl2 additive, indicating fewer trap states to reduce the nonradiative recombination. The capacitance characteristics confirm that the PbCl2 additive can largely decrease the trap states in quasi-2D perovskite films. The capacitance–voltage characteristics indicate that using the PbCl2 additive decreases the charge accumulation toward increasing the charge collection in quasi-2D perovskite solar cells. Our work indicates that the addition of PbCl2 is an effective method to improve the device performance by reducing trap states and increasing charge collection toward developing high-performance quasi-2D perovskite devices.