One-step facile synthesis of a simple carbazole-cored hole transport material for high-performance perovskite solar cells

A carbazole-based hole-transporting material named 4,4',4'',4'-(9-octylcarbazole-1,3,6,8-tetrayl) tetrakis(N,N-bis(4-methoxyphenyl) aniline) (CZ-TA) has been developed through a one-step facile synthesis approach. The solution-processed planar perovskite solar cells (PVSCs) with 50 nm thick CZ-TA hole selective layer (HSL) contributes a power conversion efficiency of 18.32%, comparable to the most commonly used 200 nm spiro-OMeTAD (18.28%) HSLs. The improved hole extraction, transport and reduced recombination are found to endow CZ-TA-based devices with impressive fill factors over 81.0%. Importantly, the unit cost of HSL in PVSCs using CZ-TA can be as low as only 1/80 of that of spiro-OMeTAD, indicating that CZ-TA could be a promising candidate as HSLs for commercialization of the low-cost PVSC technology.