Iodine vacancies (VI ) and undercoordinated Pb2+ on the surface of all-inorganic perovskite films are mainly responsible for nonradiative charge recombination. An environmentally benign material, histamine (HA), is used to passivate the VI in perovskite films. A theoretical study shows that HA bonds to the VI on the surface of the perovskite film via a Lewis base-acid interaction; an additional hydrogen bond (H-bond) strengthens such interaction owing to the favorable molecular configuration of HA. Undercoordinated Pb2+ and Pb clusters are passivated, leading to significantly reduced surface trap density and prolonged charge lifetime within the perovskite films. HA passivation also induces an upward shift of the energy band edge of the perovskite layer, facilitating interfacial hole transfer. The combination of the above raises the solar cell efficiency from 19.5 to 20.8 % under 100 mW cm-2 illumination, the highest efficiency so far for inorganic metal halide perovskite solar cells (PSCs).
Keywords: CsPbI3−xBrx; Lewis base-acid interaction; histamine; inorganic perovskite solar cells; surface passivation.
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