Addition of Diphenylamine Branches: An Efficient Approach to Highly Improve the Hole-Transporting Property of Phenylazo-Indole Components for Use in Perovskite Solar Cells

With the aim of achieving cost-effective, efficient hole transport materials (HTMs) for use in perovskite solar cells, we investigate the nature and characteristics of some materials based on phenylazo-indole (PAZI) branched by the two derivatives of diphenylamine (DPA) (-OMeDPA and -NH(2)DPA) as novel HTMs. We exploit precise computational techniques including density functional theory (DFT) and time-dependent DFT along with the Marcus theory to make an accurate estimation on the optical and electrochemical properties of the designed materials. Our results show a significant increase in the values of Stokes shift and hole mobility when the diphenylamine derivatives connect to the core (PAZI) by a phenyl group (OMeDPA-Ph-PAZI and NH(2)DPA-Ph-PAZI) instead of a direct connection. At the molecular level, Me-PAZI-5-OM. eDPA and NH2DPA-Ph-PAZI with proper HOMO levels (-5.32 and 5.34 eV) and Stokes shifts (47.61 and 111.1 nm), good stabilities (2.50 and 2.34 eV), and higher hole mobilities (6.368 X 10(-3) and 3.528 X 10(-2) cm(2) s(-1)) exhibit unique characteristics, being completely comparable to the high-cost 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'spirobifluorene as the conventional HTM. These findings indicate that the structures proposed here have remarkable potentials for use as cost-effective HTMs.