CuS nanosheets as additives in the hole transport layers for stable p-i-n perovskite solar cells

Although poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) is a widely used hole transport layer (HTL) in perovskite solar cells, its poor conductivity and the mismatched energy levels between PTAA and formamidinium-based perovskites increase interfacial carrier recombination and charge-transport resistance. To solve these problems, inorganic CuS nanosheets were synthesized and applied as additives in PTAA for the first time. After the addition of CuS, the conductivity of the HTL improves, and the energy levels are better aligned. In addition, perovskite growth is controlled through the interaction between CuS and PbI 2 , thus improving the quality of the perovskite films, which reduces nonradiative recombination. The addition of CuS into PTAA improved the power conversion efficiency from 21.99 % to 22.92 %. Moreover, both the thermal and humidity stability improved.