Organic photovoltaic performance and structural relationship of non-fullerene small molecule acceptors based on a tetraarylphenazine core and perylene diimide

Here we report a pair of perylene diimide (PDI) non-fullerene small molecular acceptors (SMAs) based on a phenazine core with either benzene or thiophene linkers. Our main design rationale is to introduce a relatively parallel orientation for PDI units by connecting two PDI units on the same side of the phenazine core. While we find that the phenazine core can introduce a parallel intramolecular orientation, it is also found that the choice of linker units also has a major influence on the molecular geometry. As a result, the two SMAs, TPPhen-4PDI and TTPhen-4PDI, exhibit very different performances. The SMA with benzene linkers, TPPhen-4PDI, can achieve a power conversion efficiency of up to 8.3%. The performance difference was also supported by a significant difference in charge mobility and GIWAXS analysis. Our work provides some important understanding on the linker influence of structural properties, and guidelines to the design of high performance PDI-based SMAs.