Silk fibroin induced homeotropic alignment of perovskite crystals toward high efficiency and stability

The photoactive lead halide perovskites with a highly crystalline structure and low trap state density were regarded as the prerequisites for achieving high photovoltaic performance. The perovskite thin films were typically synthesized by simple wet chemistry routes, where the fluctuations in the fabrication readily generate lattice defects and induce stacking faults during the crystal growth. The growth of highly crystalline and low-defect perovskite usually needs complicated synthetical manipulation and well-designed additive engineering. Here in this work, we reported a naturally available protein, silk fibroin (SF), whereby the highly ordered β-sheets component can adequately interact with perovskite intermediates and work as the crystal growth template and trap passivation agent, which induced facile self-assembly of the perovskite crystals with homeotropic alignment structure and low defect concentrations. As a result, the SF incorporated perovskite layer exhibited a much-improved conversion efficiency with charge carrier mobility 1000 times higher than that of pristine film, as well as showed robust stability under various harsh conditions.