Highly Efficient CsPbBr₃ Planar Perovskite Solar Cells via Additive Engineering with NH₄SCN

Abstract

Improving stability is a major aspect for commercial application of perovskite solar cells (PSCs). The all-inorganic CsPbBr₃ perovskite material has been proven to have excellent stability. However, the CsPbBr₃ 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 CsPbBr₃ films via additive engineering with NH₄SCN. By incorporating NH₄⁺ and pseudo-halide ion SCN^- into the precursor solution, a smooth and dense CsPbBr₃ 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 NH₄SCN additive can greatly reduce the trap state density of the CsPbBr₃ film and also effectively inhibit interface recombination and promote charge transport in the CsPbBr₃ planar PSC. Finally, the CsPbBr₃ planar PSC prepared with a molar ratio of 1.5% NH₄SCN achieves a champion efficiency of 8.47%, higher than that of the pure one (7.12%).