Novel Noncondensed Acceptors Based on 4H‐Dithieno[3,2‐B:2′, 3′‐D]pyrrole and 4H‐Cyclopenta[1,2‐B:5,4‐B′]Dithiophene N, S‐Heterocycles with an Ethynylene Linker for Ternary Polymer Solar Cells with an Efficiency More than 15%

This study explores the design, synthesis, and application of two nonfused ring nonfullerene acceptors, namely ECPDT‐IC and EDTP‐IC , featuring an ethynylene linkers between two 4Hcyclopenta[1,2‐b:5,4‐b0]dithiophene (CPDT) units and two 4‐(2‐octyldodecyl)‐4H‐dithieno[3,2‐b:2′, 3′‐d]pyrrole (DTP) units, respectively. The incorporation of the ethynylene linker is found to effectively regulate the energy levels and molecular conformations of the nonfullerene acceptors. The EDTP‐IC with a DTP central core exhibits higher electron mobility, compared to ECPDT‐IC . The frontier energy levels of both ECPDT‐IC and EDTP‐IC are aligned with PTB7‐Th and also showed complementary absorption profiles. The organic solar cells (OSCs) based on PTB7‐Th: EDTP‐IC attained higher power conversion efficiency (PCE) (13.35%) as compared to the PTB7‐Th: ECPDT‐IC counterpart (10.87%), attributed to efficient exciton dissociation and charge transport. Further, the PCE has been improved to 15.17% for ternary OSC, when ECPDT‐IC was added to PTB7‐Th: EDTP‐IC binary active layer. The PCE is about 15%, likely due to the active layer's absorption spectrum being limited to 820 nm. However, these NFR‐NFAs could be promising for efficient indoor OSCs and as guest components in OSCs with wide bandgap polymers and narrow bandgap acceptors.