A–DA′D–A Nonfullerene Acceptor Obtained by Fine-Tuning Side Chains on Pyrroles Enables PBDB-T-Based Organic Solar Cells with over 14% Efficiency
Yu Chen, Emmanuel Ν. Koukaras, Yingping Zou, Hemraj Dahiya, Ye Liu, Hui Liu, Ganesh D. Sharma
Abstract
The recent emergence of small acceptor molecules that are nonfullerene (NFSMAs) of A–DA′D–A type, particularly Y6, has accounted for the effective organic solar cells (OSCs). A new acceptor derivative denoted as Y18-DMO using 3,7-dimethyloctyl instead of 2-ethylhexyl on pyrroles of Y18 is reported. Y18-DMO shows the optical gap of 1.37 eV, with the highest occupied and lowest unoccupied molecular orbital energy levels at −5.86 and −3.90 eV, respectively. PBDB-T:Y18-DMO-based photovoltaic devices treated for 40 s by solvent vapor annealing in tetrahydrofuran (THF) yield a power conversion efficiency that reaches 14.18%, which is around the maximum efficiencies among the PBDB-T-based OSCs so far. Besides, these devices exhibit an energy loss as low as 0.55 eV while achieving a large open-circuit voltage of 0.81 V.