Simultaneous enhancement of short-circuit current density, open circuit voltage and fill factor in ternary organic solar cells based on PTB7-Th:IT-M:PC71BM

Recently, studies on ternary organic solar cells (OSCs) have revealed their potentials for achieving the improved device performances. However, owing to the trade-off between the short-circuit current density JSC) and open circuit voltage (VOC), the mismatch of the energy levels between donors and acceptors leads to a large energy loss and then leads to a lower VOC in most ternary systems. In this study, we incorporated 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)− 5-methylindanone)− 5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b']-dithiophene (IT-M) into a PTB7-Th:PC71BM host system as the third component, which has a higher energy level of the lowest unoccupied molecular orbital (LUMO) than that of PC71BM. The introduction of IT-M adjusts the energy-level cascade, enhances the absorption intensity and modulates the film morphology, which facilitate the charge generation, enhance the charge transport, and suppress the charge recombination, as manifested by the significantly enhanced VOC, JSC, and fill factor (FF). Therefore, the results indicate that a simultaneous enhancement of VOC, JSC, and FF can be achieved by incorporation of IT-M in ternary OSCs, providing a higher efficiency.