A star-shaped carbazole-based hole-transporting material with triphenylamine side arms for perovskite solar cells

Herein, we employ a simple star-shaped hole-transporting material (HTM) consisting of a carbazole core and triphenylamine side arms, termed LD29, in mesoscopic perovskite solar cells (PSCs). LD29 exhibits a deep HOMO level of -5.24 eV, a high hole mobility of 1.72 x 10(-5) cm(2) V-1 s(-1), and a relatively high glass-transition temperature of 121 degrees C, as well as good film-forming ability. PSCs using dopant-free LD29 as the HTM layer exhibit a maximum efficiency of 14.29%. Promisingly, when LD29 is doped, a champion efficiency over 18% has been achieved, which is even comparable with that of the conventional doped spiro-OMeTAD. Moreover, the laboratory synthesis cost for LD29 is significantly lower than that for spiro-OMeTAD. Importantly, the PSC performance does not change greatly with the concentration of LD29 regardless of whether the dopants are used, which has the potential to further reduce material usage. The device employing LD29 also shows comparable stability to that employing spiro-OMeTAD. Consequently, our results provide an important step forward for the commercialized application of PSCs.