Comparative Study of Linear and Starburst Ethane-Based Hole-Transporting Materials for Perovskite Solar Cells

Recently, linear and starburst hole-transporting materials (HTMs) have been widely developed as potential alternatives to conventional spiro-OMeTAD in perovskite solar cells (PSCs). Herein, two facile ethane-based HTMs with a linear or starburst shape have been designed and prepared. The molecular structure variations in the photophysical, electrochemical, hole mobility, hydrophobicity, and film-forming, and photovoltaic properties in PSCs are comprehensively investigated. Interestingly, the linear molecule exhibits bathochromic-shift spectra, slightly lower highest occupied molecular orbital (HOMO) energy level, higher hole mobility, and better hydrophobicity than its starburst counterpart. Moreover, photoluminescence study confirmed that the linear molecule rather than the starburst molecule can efficiently extract holes at the perovskite/HTM interface. Consequently, higher efficiency of 16.85% for a doped linear-molecule-based device is obtained compared to that of a starburst counterpart exhibiting a lower efficiency of 14.87%. Moreover, the linear HTM also shows better stability. These results indicate the better application potential of linear HTMs than that of the starburst ones.