Perovskite Solar Cells Employing Copper Phthalocyanine Hole-Transport Material with an Efficiency over 20% and Excellent Thermal Stability

We investigate the properties of an inexpensive hole-transporting material (HTM), copper phthalocyanine (CuPc), deposited by a solution-processing method in perovskite solar cells (PSCs). Cracks are found to be abundant on the as-deposited CuPc films, which lead to serious shunts and interface recombination. Surprisingly, shunts and interface recombination are significantly reduced and cell performance is greatly improved after heat treatment at 85 °C. We find that the enhancement is due to heat-induced migration of Au particles away from the cracks. Furthermore, Au is found to dope the CuPc film, and the doping effect is greatly enhanced by the heat treatment. Using CuPc and quadruple-cation perovskite, an efficiency of over 20% and negligible hysteresis is achieved after the heat treatment, which is the highest value reported for this structure. Additionally, PSCs employing CuPc and dual-cation perovskite show excellent thermal stability after >2000 h at 85 °C and good light stability at 25 °C.