Sulfur vacancy defects healing of WS2 quantum dots boosted hole extraction for all-inorganic perovskite solar cells

The promotion of interfacial charge transfer and extraction plays an important role in further improving the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Herein, a composite of WS2/AgIn5S8 quantum dots (QDs) with lattice matching and suitable energy level is launched as an efficient hole extractor for carbon-based all-inorganic CsPbBr3 PSCs. Due to the sulfur vacancy defects passivation of WS2 QDs by AgIn5S8 QDs and a Type-II band alignment between them, a boosted hole extraction and transfer is realized. In addition, the strong interaction of S of WS2/AgIn5S8 QDs and the Pb of perovskite film constructs a convenient pathway of hole transport to promote hole transfer and heals the surface lead ions defects of perovskite film, and the uncoordinated bromine ions defects of CsPbBr3 film are also passivated by the WS2/AgIn5S8 QDs in the form of Ag-Br and In-Br bonds, leading to an inhibition of charge recombination. As a result, the carbon-based all-inorganic CsPbBr3 PSCs with WS2/AgIn5S8 QDs free of encapsulation deliver a maximum PCE of 10.24 % and a remarkably improved stability with over 93 % retention of the initial efficiency after being stored in air with high humidity and temperature (85 % RH, 85 °C) for 720 h.