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 CuInS 2 film between perovskite and Spiro-OMeTAD (Spiro) layers. The power conversion efficiency (PCE) of the perovskite solar cells (PSCs) with double-layered HTM of CuInS 2 /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 CuInS 2 /Spiro was enhanced. The PCE of the PSCs with CuInS 2 /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 CuInS 2 and Spiro, fast hole extraction and transport, and decreased charge recombination in the PSCs with double-layered HTM of CuInS 2 /Spiro. This work provides a promising prospect to design a low-cost and high stability HTM for commercial PSCs.