An efficient phenylaminecarbazole-based three-dimensional hole-transporting materials for high-stability perovskite solar cells

Hole-transport materials (HTMs) are the key material for preparing high-performing perovskite solar cells (PSCs). Herein, we present a novel and efficient hole-transporting material, 9,9-dioctyl fluorenyl phenylamine carbazole linked methoxy triphenylamines (CzPAF-OMeTAD), which was synthesized via Buchwald-Hartwig amination reactions from very cheap raw materials such as phenylcarbazole with 9,9-dioctyl fluorene bridge and arylamine terminals. It is demonstrated the synthesized CzPAF-OMeTAD with 9,9-dioctyl fluorene as bridge shows a higher hydrophobic and further induce a higher water contact angle of 91 degrees relative to that (79 degrees) for commonly SpiroOMeTAD with spirofluorene linked methoxy triphenylamines. Further, CzPAF-OMeTAD also exhibits a deeper highest occupied molecular orbital (HOMO) energy level of -5.30 eV and a higher hole mobility of 3.83 x 10-5 cm(2)V(-1)S(-1), indicating a potential hole-transport material for high-performance perovskite solar cells. Thus, PSCs were fabricated by using the CzPAF-OMeTAD as HTMs, and the resulting cell demonstrates a high power conversion efficiency (PCE) of 15.35% and very high stability. For example, after 20 days of aging with relative humidity of 60%, the PCE still exhibit retention more than 87% of their initial values for corresponding cell. These are ascribed to the improved film-forming ability by sufficient amount of alkyl chains in CzPAF-OMeTAD and a higher hole-mobility for CzPAF-OMeTAD. These results implied our current research provides huge potential direction in the development of highly efficient and stable PSCs with further optimizing HTMs in the future.