Dual-Additive-Driven Morphology Optimization for Solvent-Annealing-Free All-Small-Molecule Organic Solar Cells

摘要

All-small-molecule organic solar cells (ASM-OSCs), which consist ofsmall-molecule donors and acceptors, have recently been studied extensivelyto eliminate the batch-to-batch variation from polymer-based donor oracceptor. On the other hand, the control of their active layer morphology ismore challenging due to the similar chemical structure and miscibility ofsmall-molecule donor and small-molecule accepter. Hence, this studydevelops a dual-additive-driven morphology optimization method forASM-OSCs based on BTR-Cl:Y6. One solid additive – 1,4-diiodobenzene (DIB)and one liquid additive – diiodomethane (DIM) are selected, making use oftheir distinct interaction mechanisms with Y6 and BTR-Cl. It is found that DIBcan form a eutectic phase with Y6, which can increase the intermolecularinteractions and modulate the acceptor phase separation, while thesimultaneous volatilization of DIM suppresses the over-aggregation of BTR-Clduring the film casting process. As a result of the synergistic morphologytuning, the optimized device delivers a power conversion efficiency (PCE) ashigh as 15.2, among the highest PCE reported to date for binary ASM-OSCswithout solvent annealing treatment. This work demonstrates the potential ofmorphology tuning via the incorporation of dual additives into ASM-OSCs,enabling them to achieve comparable efficiencies to those of conventionalpolymer/small-molecule based OSCs.