Self-crosslinking strategy enabling high-performance inverted inorganic perovskite solar cells with fill factor exceeding 85%

Abstract

Inorganic CsPbI₃ perovskite with superior thermal stability and photoelectric properties has developed into a promising candidate for photovoltaic applications. Nevertheless, the power conversion efficiency (PCE) of CsPbI₃ perovskite solar cells (PSCs) still lags far behind that of both organic-inorganic hybrid counterparts and the theoretical PCE limit, primarily restricted by severe fill factor (FF) and open-circuit voltage (V_OC) deficits. Herein, an in-situ self-crosslinking strategy is proposed to construct high-performance inverted inorganic PSCs by incorporating acrylate monomers as additives into CsPbI₃ perovskite precursors. During the thermal annealing process of perovskite films, acrylate monomers can form network structures by breaking the C=C groups through an in-situ polymerization reaction, mainly anchored at the grain boundaries (GBs) and on the surfaces of perovskite. Meanwhile, the C=O groups of acrylate polymers can favorably coordinate with uncoordinated Pb²⁺, thereby decreasing defect density and stabilizing the perovskite phase. Particularly, with multiple crosslinking and passivation sites, the incorporation of dipentaerythritol pentaacrylate (DPHA) can effectively improve the perovskite film quality, suppress nonradiative recombination, and block moisture erosion. Consequently, the DPHA-based PSC achieves a champion PCE of 20.05% with a record-high FF of 85.05%, both of which rank among the top in the performance of inverted CsPbI₃ PSCs. Moreover, the unencapsulated DPHA-based device exhibits negligible hysteresis, remarkably improved long-term storage, and operational stability. This work offers a facile and useful strategy to simultaneously promote the efficiency and device stability of inverted inorganic PSCs.