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.