Modulating intermolecular interactions by collaborative material design to realize THF-processed organic photovoltaic with 1.3 V open-circuit voltage

Achieving efficient exciton dissociation and high power conversion efficiency (PCE) becomes a great challenge when the open-circuit voltage (V-OC) of organic photovoltaics (OPVs) reaches an upper limit value of 1.3 V or higher. The balanced intermolecular interactions of donor/donor (D/D), acceptor/acceptor (A/A) and donor/acceptor (D/A) determine the molecular stacking, crystallinity, morphology and subsequent exciton dissociation, but there is a lack of relevant material design guidelines to simultaneously modulate the three interactions. Herein, we rationally design a terpolymer E18 by introducing a 20% proportion of the side chain with a chlorine atom and bulky alkyl chain to the classic p-type polymer D18, and we also obtain a non-fullerene acceptor BTA3-4F by adding four fluorine atoms on the side chain of the middle D unit of A(2)-A(1)-D-A(1)-A(2) type molecule BTA3. As expected, the collaborative material design guarantees that E18:BTA3-4F achieves the balanced A/A, D/D and D/A intermolecular interactions in the blend film, resulting in tighter large-area molecular stacking and excellent vertical phase separation. Thus, the nonhalogenated solvent tetrahydrofuran (THF) processed OPV device based on E18:BTA3-4F realizes the highest PCE of 10.03% with a V-OC of 1.30 V and a non-radiative energy loss (?E-3) of 0.18 eV. In contrast, the E18:BTA3 combination exhibits a V-OC of 1.32 V and a ?E-3 of 0.12 eV with an inferior PCE of 4.98%. Our results provide wide bandgap material design guidelines to optimize intermolecular interactions, and thus realize efficient exciton dissociation for the OPV devices with a V-OC of 1.3 V or higher.

Automated summary

Efficient exciton dissociation and high power conversion efficiency are achieved in organic photovoltaics (OPVs) with a V-OC of 1.3 V or higher through rational material design. The collaborative design of terpolymer E18 and non-fullerene acceptor BTA3-4F ensures balanced intermolecular interactions, resulting in tighter molecular stacking and excellent phase separation. These results provide material design guidelines for optimizing intermolecular interactions and achieving efficient exciton dissociation in OPV devices with a V-OC of 1.3 V or higher.