Interface Engineering for Inverted Perovskite Solar Cells via Cooperative Passivation of Bimolecular Additives to Achieve Low Voltage Loss

ABSTRACT The performance of inverted p‐i‐n type perovskite solar cells (IPSCs) is limited by non‐radiative recombination caused by surface defects on the perovskite layer, which in turn leads to a loss of open‐circuit voltage ( V _OC ). In this study, a novel synergistic passivation strategy is proposed, which leverages the synergy between piperazine dihydriodide (PDI) and methylammonium iodide (MAI) to modify the perovskite/C ₆₀ interface in IPSCs effectively. This strategy fully utilizes the multiple structural and functional advantages of PDI. Its alkyl core‐electron cloud‐rich‐NH terminal can effectively coordinate with deep‐level defects, and the piperazine ring can interact with the FA ⁺ ions, inhibiting their migration. Furthermore, MAI, due to its small molecular size, can penetrate the perovskite surface and repair iodine vacancies ( V _I ). It also compensates for the deficiency of organic cations, achieving the ideal stoichiometric composition and enhancing interfacial contact. As a result, this synergistic strategy enhances energy level alignment, significantly suppresses non‐radiative recombination at the perovskite/C ₆₀ interface, and improves carrier transport efficiency. The optimized PSC based on this strategy achieves a high V _OC of 1.23 V (the theoretical limit for a 1.58 eV bandgap is 1.31 V, corresponding to a voltage deficit of only 0.08 V) and a PCE of 25.74%, and exhibits excellent long‐term operational stability.