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 WS 2 /AgIn 5 S 8 quantum dots (QDs) with lattice matching and suitable energy level is launched as an efficient hole extractor for carbon-based all-inorganic CsPbBr 3 PSCs. Due to the sulfur vacancy defects passivation of WS 2 QDs by AgIn 5 S 8 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 WS 2 /AgIn 5 S 8 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 CsPbBr 3 film are also passivated by the WS 2 /AgIn 5 S 8 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 CsPbBr 3 PSCs with WS 2 /AgIn 5 S 8 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.