Researchers from Peking University, China Automotive Technology and Research Center, Beijing Institute of Technology and Jiangnan University recently demonstrated the ability of tuning the Fermi level of the hole transport layer (HTL) to reduce the energy level difference (Schottky barrier) between HTLs and Cu. In addition, the team identified that the balance of energy level difference between HTL and adjacent layers (including perovskite and Cu) is crucial to efficient carrier transportation and photovoltaic performance improvement in the PSCs.

The team's effort was aimed at addressing the challenge of developing low-cost and stable metal electrodes, which could be very important for mass production of perovskite solar cells (PSCs). As an earth-abundant element, Cu becomes an alternative candidate to replace noble metal electrodes such as Au and Ag, due to its comparable physiochemical properties with simultaneously good stability and low cost. However, the undesirable band alignment associated with the device architecture impedes the exploration of efficient Cu-based n-i-p PSCs.