Enhancing efficiency and stability of inverted perovskite solar cells through synergistic suppression of multiple defects via poly(ionic liquid)-buried interface modification

The stability of perovskite solar cells (PSCs) is adversely affected by nonradiative recombination resulting from buried interface defects. Herein, we synthesize a polyionic liquid, poly(p-vinylbenzyl trimethylammonium hexafluorophosphate) (PTA), and introduce it into the buried interface of PSCs. The quaternary ammonium cation (N(–CH₃)₃⁺) in PTA can fill the vacancies of organic cations within the perovskite structure and reduce shallow energy level defects. Additionally, the hexafluorophosphate (PF₆⁻) in PTA forms a Lewis acid-base interaction with Pb²⁺ in the perovskite layer, effectively passivating deep energy level defects. Furthermore, hydrogen bonding can be established between organic cations and the PF₆⁻ anion, preventing the formation of shallow energy level defects. Through this synergistic mechanism, the deep and shallow energy level defects are effectively mitigated, resulting in improved device performance. As a result, the resulting treated inverted PSC exhibits an impressive power conversion efficiency (PCE) of 24.72 %. Notably, the PTA-treated PSCs exhibit remarkable stability, with 88.5 % of the original PCE retained after undergoing heat aging at 85 °C for 1078 h, and 89.1 % of the initial PCE maintained following continuous exposure to light for 1100 h at the maximum power point. Synergistically suppressing multiple defects at the buried interface through the use of polyionic liquids is a promising way to improve the commercial viability of PSCs.