A Simple Carbazole-Triphenylamine Hole Transport Material for Perovskite Solar Cells

In this work, a simple carbazole-based hole transport material with triphenylamine moieties, termed LD22, has been used in perovskite solar cells (PSCs). It is noted that LD22 exhibits a proper HOMO level of -5.27 eV, high hole mobility of 1.65 X 10(-5) cm(2) V-1 s(-1), and relatively high glass-transition temperature of 132 degrees C. When LD22 was used in PSCs, pristine LD22-based PSCs showed a power conversion efficiency (PCE) of 13.04%. When LD22 is doped, the PCE improves to a promising 17.18%. More importantly, the concentration of LD22 has little influence on the PSC performance regardless of the existence of dopants, which shows good repeatability. As a reference, the device with doped 2,2',7,7'-tetrakis(N,N-bis(4-methoxyphenyl)amino)-9,9'-spiro-bifluorene (spiro-OMeTAD) shows a PCE of 17.73%. On the other hand, the laboratory synthesis cost of LD22 is much lower than that of spiro-OMeTAD. Therefore, the results indicate that the simple carbazole-triphenylamine compounds own the potential to be doped-free HTM and LD22 could be a promising HTM candidate for high-performance PSCs due to its simple structure.