Gold atom diffusion assisted thermal healing enabling high-performance hole-transporting material in solar cells

The use of the compact hole-transporting layer (HTL) with strong hole extraction ability is vital to prepare high-efficiency solar cells. Here, we report the application of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) doped copper phthalocyanine (CuPc) as the hole-transporting layer for the Sb2(S,Se)3 solar cells. We find that the diffusion of gold atoms into the copper phthalocyanine film is able to heal the cracks and pinholes of the CuPc film, which enables the morphology to become more flat and denser, along with enhanced hole mobility. Benefitting from these results, the F4-TCNQ doped CuPc-based Sb2(S,Se)3 solar cells achieved best power conversion efficiency of 8.57%. More importantly, the device based on F4-TCNQ doped CuPc HTL showed essentially improved operational stability under the condition of 85% humidity and 85 °C. This research provides a suitable method for improving the morphology and transport properties of the CuPc based hole-transporting layer for solar cell and other optoelectronic device applications.