Silicon Phthalocyanine-Engineered Ammonium Cations for Heterointerface Reinforcement toward Thermally Stable Perovskite Solar Cells

Passivation treatment for perovskite films has constituted an indispensable process in fabricating high-performance perovskite solar cells (PSCs), yet the degradation or dynamic evolution of passivation layers under external stimuli persists as a critical bottleneck impeding commercialization. Here, we develop a silicon phthalocyanine-engineered ammonium cation (SiPc(4HTy)2) that enables perovskite films to resist degradation under thermal stress and meanwhile reinforces the related heterointerfaces in PSCs. The surface passivation strategy based on SiPc(4HTy)2 efficiently reduces surface defects of perovskite films, optimizes energy level alignment, and suppresses ion diffusion, without relying on the formation of two-dimensional perovskite passivation layers. The superior passivation efficacy originates from the solution-processable bulky cation engineering achieved by axially coordinating three-dimensional silicon phthalocyanine. Under the passivation treatment of SiPc(4HTy)2, the power conversion efficiency of PSCs reaches a maximum of 23.55%, mainly due to the improvement of the open-circuit voltage and fill factor. Furthermore, benefiting from the maintenance of the morphology and optoelectronic properties of perovskite films, the related devices still maintain more than 80% of their initial performance after over 1000 h at 85 °C in an inert atmosphere.