Highly Efficient CsPbBr Planar Perovskite Solar Cells via Additive Engineering with NHSCN.

Improving stability is a major aspect for commercial application of perovskite solar cells (PSCs). The all-inorganic CsPbBr perovskite material has been proven to have excellent stability. However, the CsPbBr film has a small range of light absorption and serious charge recombination at the interface or inside the device, so the power conversion efficiency is still lower than that of the organic-inorganic hybrid one. Here, we successfully fabricate high-quality CsPbBr films via additive engineering with NHSCN. By incorporating NH and pseudo-halide ion SCN into the precursor solution, a smooth and dense CsPbBr film with good crystallinity and low trap state density can be obtained. At the same time, the results of a series of photoluminescence and electrochemical analyses including electrical impedance spectroscopy, space-charge limited current method, Mott-Schottky data, and so on reveal that the NHSCN additive can greatly reduce the trap state density of the CsPbBr film and also effectively inhibit interface recombination and promote charge transport in the CsPbBr planar PSC. Finally, the CsPbBr planar PSC prepared with a molar ratio of 1.5% NHSCN achieves a champion efficiency of 8.47%, higher than that of the pure one (7.12%).