Thermal Stability of CuSCN Hole Conductor-Based Perovskite Solar Cells

Although perovskite solar cells (PSCs) surpassing 20 % in certified power conversion efficiency (PCE) have been demonstrated with organic hole-transporting layers (HTLs), thermal degradation remains one of the key issues for practical applications. We fabricated PSCs using low temperature solution-processed CuSCN as the inorganic hole-transport layer (HTL), which possesses a highly stable crystalline structure and is robust even at high temperatures. The best-performing cell delivers a PCE of 18.0 %, with 15.9 % measured at the stabilized power output. Here we report the thermal stability of PSCs based on CuSCN in comparison with commonly used 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD). The PSC fabricated with organic spiro-OMeTAD degrades to 25 % of initial PCE after annealing for 2 h at 125 °C in air under 40 % average relative humidity. However, CuSCN-based PSCs maintain approximately 60 % of the initial value, exhibiting superior thermal stability under identical conditions. This work demonstrates that high efficiency and improved thermal stability are simultaneously achieved when CuSCN is used as an HTL in PSCs.