Treatment of Perovskite Solar Cells by Complementary Cyclic Ammonium Agents

Interfacial defect heterogeneity and insufficient passivation are major sources of nonradiative recombination losses in perovskite solar cells (PSCs). They not only increase carrier recombination but also perturb local band alignment. Here, a complementary cyclic ammonium passivation strategy mixing conjugated and nonconjugated agents is developed to simultaneously achieve homogeneous defect passivation and interface optimization in inverted PSCs. Especially, by combining piperazinium diiodide and 2-thiophenemethylammonium iodide, a synergistic passivation architecture is established that effectively homogenizes the interfacial electrostatic landscape while mixing passivating functional groups. Quasi-Fermi level splitting (QFLS) analysis combined with spatially resolved surface photovoltage (SPV) characterizations reveal that piperazine-dependent Voc losses originate from heterogeneous SPV distributions, whereas the complementary passivation strategy produces a highly uniform and enhanced SPV response across the perovskite film. The resulting uniform electrostatic environment suppresses nonradiative recombination, reduces the QFLS-VOC mismatch, and promotes efficient charge extraction. This strategy leads to stable PSC with a champion power conversion efficiency (PCE) of 27.18% with a certified steady-state PCE of 26.47%.