Tetrabenzotriazacorrole and its derivatives as undoped hole transporting materials for perovskite solar cells: Synthesis, device fabrication, and device performance

Abstract

Abstract Phosphorous tetrabenzotriazacorrole (TBC) and its two soluble derivatives (TBC-1 and TBC-2) were synthesized and used for the first time as undoped hole transporting materials (HTMs) in MAPbI3 perovskite solar cells (PSCs). Their performance in PSCs was measured and compared with that of Spiro-OMeTAD and phthalocyanine precursor. The fundamental properties related to HTMs are also examined. These novel HTMs are easily prepared, cost-effective, and solution processable. The materials exhibited much higher hole transport mobility and broader light absorption than pristine Spiro-OMeTAD and phthalocyanine precursor. They can work efficiently in the absence of any dopant for devices composed of FTO/cp-TiO2/mp-TiO2/MAPbI3/HTM/Au. The undoped mesoscopic solar cell devices based on TBC exhibited a promising power conversion efficiency (PCE) of up to 16.2% (measured at 100 mW cm2 illumination, AM 1.5 G), together with good long-term stability under ambient conditions. This PCE of 16.2% observed using TBC is remarkably higher than the 11.2% observed using undoped Spiro-OMeTAD and also much better than the 8.70% observed using its phthalocyanine precursor. As to substitution effects, α-substituted TBC-1 was found to be a better HTM than β-substituted TBC-2 (PCE 11.4%) and unsubstituted TBC-3 (PCE 6.81%) under the same conditions. These results provide the basis for further exploiting TBC compounds as a new type of low-cost and effective HTM for PSCs.