A comparative study of a fluorene-based non-fullerene electron acceptor and PC61BM in an organic solar cell at a quantum chemical level

Abstract

The importance of developing non-fullerene acceptors has been emphasized to overcome the drawbacks of fullerene derivatives such as limited light absorption, poor solubility and high cost. In this study, we present a comparative theoretical study on the organic solar cell (OSC) performance of a fluorine-based non-fullerene acceptor FENIDT and the representative fullerene derivatives, PC₆₁BM, based on the dependent/time-dependent density functional theory (DFT/TDDFT) calculations. Remarkably, according to the investigation on relevant parameters with OSC performance, FENIDT not only shows a much higher charge separation rate and lower recombination rate at the donor/acceptor interface, but also possesses a larger open circuit voltage and better electron mobility than that of PC₆₁BM, which suggests that FENIDT might be more suitable as an acceptor material. Some speculations were provided to explain the superiority of PC₆₁BM in experiments such as the simplified model method. Moreover, according to the advantages of FENIDT, a series of acceptors were designed. The results illustrate that the designed molecule 3 with a p-phenylenediamine unit based on the FENIDT shows better performance than others and may act as a promising acceptor material for OSCs. Finally, we hope our investigations in this study could provide a theoretical guideline of further optimization of the acceptor materials for OSCs.