Oligomeric Silica-Wrapped Perovskites Enable Synchronous Defect Passivation and Grain Stabilization for Efficient and Stable Perovskite Photovoltaics
The intrinsic instability of hybrid perovskite materials induced by defect states arises as one major challenge hampering the commercialization of perovskite solar cells (PSCs). Here, we report a facile strategy of wrapping perovskite grains within an oligomeric silica (OS) matrix in a core-shell geometry, which can synchronously passivate the defects at surfaces and grain boundaries and stabilize the grains at the nanoscale. We observe a significant reduction of trap density and elongation of carrier lifetime in OS-wrapped perovskites, which yields an increased efficiency of 21.5% for p-i-n structured PSCs with a decent open-circuit voltage of 1.15 V and a fill factor of 0.81. This all-around nanoscale grain wrapping leads to remarkable improvement of the operational stability of PSCs, sustaining 80% of the efficiency after "burn-in" under full sunlight with UV for more than 5200 h. Our findings provide a new pathway towards efficient and stable PSCs.