Exploring more effective polymer donors for the famous non-fullerene acceptor ITIC in organic solar cells by increasing electron-withdrawing ability

Abstract

Abstract Recently, the non-fullerene acceptor ITIC has attracted a lot of attention in terms of its prominent performance in organic solar cell (OSC). A better match with the donor materials is critical for it, so we on one hand compared the match of two typical donors PBDB-T and PBQ-0F with ITIC trying to find the main difference between them. On the other hand, we designed two donors 1 and 2 based on the same 2D-BDT unit and estimated their cell efficiency aiming to explore more effective donors for ITIC. The molecular dynamics simulation was carried out to get more practical photovoltaic interface, and the density functional theory was employed to estimate the cell efficiency. It is found that PBDB-T not only exhibits higher charge separation efficiency depending on larger charge separation and smaller charge recombination rates than PBQ-0F, but also displays stronger electron-hole coherence from donor to acceptor fragments at its S1 state than PBQ-0F indicating its easier exciton dissociation at excited states. The stronger electron-withdrawing ability of the acceptor fragment in PBDB-T is concluded to make the main contribution to its higher charge separation efficiency, which is further proved by our designed donors 1 and 2. Molecule 2 with stronger electron-withdrawing ability of the acceptor fragment than PBDB-T shows better charge separation performance at the interface than PBDB-T, which again suggests introducing strong electron-withdrawing group in this kind of donors may be a good choice for improving the performance of organic solar cell using ITIC as acceptor.