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

Quasi-2D Ruddlesden-Popper perovskites (RPPs) exhibit excellent photo/environmental-stability. However, the main drawback is their relatively low photovoltaic properties compared with three-dimensional (3D) 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 shows the optimized device performance over 15%, and devices exhibit much-improved humidity stability. Upon PbCl2 addition, the quasi-2D perovskites have larger and more compact grains, which form high quality of films. The photoluminescence gives rise to a much prolonged lifetime under the PbCl2 additive, indicating fewer trap states to reduce the non-radiative recombination. The capacitance characteristics confirm that the PbCl2 additive can largely decrease the trap states in quasi-2D perovskite films. The capacitance-voltage (C-V) characteristics indicate that using PbCl2 additive decreases the charge accumulation towards increasing th...