Polymeric non-fullerene acceptors offer the potential to restrict the self-aggregation that is typical for small molecule non-fullerene acceptors, which potentially yields this fine structured morphology. But phase separation is seen to be restricted. To be able to unstand this, we studied a blend of the polymeric acceptor PF5-Y5 and the donor polymer PBDB-T to investigate the molecular interactions in solution in a joint experimental-theoretical spectroscopy study. Solar cells prepared of this blend have reached power conversion efficiencies of over 14%.(1) From absorption spectroscopy of the PBDB-T:PF5-Y5 blend solutions at increasing temperatures, combined with concentration-dependent fluorescence spectroscopy and excitation spectroscopy, we could conclude that in addition to temperature-induced disaggregation of both donor and acceptor polymers, donor-acceptor complexes are formed in dilute blend solutions of PBDB-T and PF5-Y5. The formation of the donor-acceptor complexes competes with the donor and acceptor self-aggregation and the solvent environment is found to influence these interactions. Our results show also that the donor-acceptor polymer complexes are stabilized in more polar solvents. The near IR-region of the absorption spectrum could be matched with the calculated electronic excitations of donor-acceptor complexes of PBDB-T and PF5-Y5 oligomers. These pre-formed donor-acceptor complexes in solution can be expected to have important consequences on the resulting film morphology. These insights are also expected to direct the future design of compatible donor-acceptor polymer pairs for high-performance all-polymer solar cells.

Donor-acceptor polymer hybridization forming a complex in solution behind highly efficient all-polymer solar cells

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.