Molecularly Engineered Hole-Transport Material for Low-cost Perovskite Solar Cells
Triphenylamine-N-phenyl-4-(phenyldiazenyl)aniline (TPA-AZO) is synthetized via a facile CuI-catalyzed reaction and used as hole transport material (HTM) in perovskite solar cells (PSCs), as alternative to the expensive spiro-type molecular materials, including commercial 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD). Experimental and computational investigations reveal that the highest occupied molecule orbital (HOMO) level of the TPA-AZO is deeper than the one of the spiro-OMeTAD, and optimally matches with the conduction band of the perovskite light absorber. The use of TPA-AZO as HTM results in PSC prototypes with a power conversion efficiency (PCE) approaching the one of the spiro-OMeTAD-based reference device (17.86% vs. 19.07%). Moreover, the use of inexpensive starting reagents for the synthesis of the TPA-AZO makes the latter a new affordable HTM for PSCs. In particular, the cost of 1 g of TPA-AZO ($22.76) is significantly lower compared to the one of spiro-OMeTAD ($170-475). Overall, the TPA-AZO-based HTMs are promising candidates for the implementation of viable PSCs in large-scale production.