Effect of the donor unit heterocyclic substitution strategy on the performance of ZnII porphyrin-based hole transport materials

Abstract

Hole transport materials (HTMs) are instrumental in determining the performance and stability of perovskite solar cells (PSCs). Consequently, it is essential to develop suitable HTMs that can effectively facilitate hole extraction and transport within PSCs. In this study, we conducted theoretical investigations utilizing quantum chemistry methods on the promising HTM molecule YZT1, which features a diacetylene-based Zn^II porphyrin as its core moiety and dibutyl aniline as the donor moiety on either side. We designed new molecules by substituting the benzene ring with heterocyclic rings, designated as YZT1-Z1–YZT1-Z6. The impact of four distinct donor units—benzene, pyridine, pyran, and thiapyran—on the molecular photoelectric properties and charge transport capabilities was examined. The findings suggest that the HOMO of these investigated molecules exceeds the valence band energy of perovskite materials. Furthermore, it was observed that the HOMO levels of the new molecules are found to be lower than that of YZT1, signifying their excellent ability for hole extraction. All newly designed molecules exhibit blue-shifted maximum absorption wavelengths compared to YZT1. Notably, both YZT1-Z1 and YZT1-Z2 demonstrate significant enhancements in hole mobility relative to the previously experimentally characterized molecule YZT1; among them, YZT1-Z1 exhibits the highest hole mobility. It is particularly noteworthy that both YZT1-Z1 and YZT1-Z2 show superior overall performance when compared to other molecules.