Efficient Non-Fullerene Solar Cells Enabled by a Temperature-Dependent Terpolymer with Controlled Aggregation and Orientation

Abstract

Light harvesting, molecular aggregation, and orientation of photoactive materials are crucial for non-fullerene polymer solar cells. Random copolymerization is a feasible and effective way to modify the molecular structure of polymer donors. However, it is very challenging to transfer the edge-on orientation of oligothiophene-based polymers to face-on orientation. Herein, we employed random copolymerization strategy by incorporating a specific ratio of a benzo­[1,2-c:4,5-c′]­dithiophene-4,8-dione (BDD)-based monomer into the backbone of a temperature-dependent polymer PFBT4T to improve the device performance. The resulting terpolymer donor PFBT4T-T20 with a comparable synthetic complexity possesses a dominant face-on orientation and weakened aggregations in solution and film, which are different from the parent polymer PFBT4T. When blended with acceptor Y14, the PFBT4T-T20-based device exhibits a more balanced carrier transport and optimal morphology and then achieved a higher efficiency of 15.60%. Our results reveal that the terpolymer strategy involving an extra component of the C2v symmetric structure can revive the oligothiophene-based conjugated polymer toward efficient non-fullerene solar cells.

Dithienoquinoxaline-quaterthiophene wide bandgap donor polymers with strong interchain aggregation for efficient organic solar cells processed with a non-halogenated solvent

“…Therefore, the most balanced charge transport with m h /m e close to 1 was achieved when the processing temperature was 60 °C, which would be benecial to suppress charge recombination. 53,54 Transient photocurrent (TPC) and transient photovoltage (TPV) decay kinetics were investigated to reveal the charge extraction and recombination processes of the TL-processed OSCs. The processing temperature of 60 °C for the PQx4T-2F:Y14 active layer can endow the resulting OSCs with the shortest charge sweep-out time at short-circuit conditions of 0.120 ms during the TPC measurements (Fig.…”

“…Therefore, the most balanced charge transport with μ h / μ e close to 1 was achieved when the processing temperature was 60 °C, which would be beneficial to suppress charge recombination. 53,54…”