Interface Engineering for Inverted Perovskite Solar Cells via Cooperative Passivation of Bimolecular Additives to...

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/C₆₀ 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/C₆₀ 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.