Double-layered hole transport material of CuInS2/Spiro for highly efficient and stable perovskite solar cells

In this paper, double-layered hole transport material (HTM) was designed and fabricated by adding a thin CuInS2 film between perovskite and Spiro-OMeTAD (Spiro) layers. The power conversion efficiency (PCE) of the perovskite solar cells (PSCs) with double-layered HTM of CuInS2/Spiro was improved to 19.63% from 17.97% for the devices with pure Spiro. Moreover, the operational stability of the PSCs with double-layered HTM of CuInS2/Spiro was enhanced. The PCE of the PSCs with CuInS2/Spiro retains 91% of the initial value after 30 days storage in ambient atmosphere. The experimental results indicate that the improved performance could be come from the energy band match between CuInS2 and Spiro, fast hole extraction and transport, and decreased charge recombination in the PSCs with double-layered HTM of CuInS2/Spiro. This work provides a promising prospect to design a low-cost and high stability HTM for commercial PSCs.