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.