Dithienopyrrolothiophene (DTPT) based acceptors for fine-tuning molecular packing and enhancing ternary organic photovoltaic performance

The ternary strategy boosts the performance of organic photovoltaics (OPVs) by optimizing light-harvesting, blend morphology, and energy level alignment. Three novel non-fullerene acceptors (NFAs), IN-DTPT-b20 (1), INF-DTPT-b20 (2), and INCl-DTPT-b20 (3), have been designed and synthesized. These NFAs feature a dithienopyrrolothiophene (DTPT)-based fused ring core with soluble branched alkyl side chains and indanone-based end groups, which are functionalized with different halogens (H, F, Cl) to modulate the electronic properties of the NFAs. A comparative study of the thermal, optical, electrochemical, and computed electronic structural properties of compounds 1-3 was conducted. We investigated the optoelectronic properties of PM6:Y6 based OPV in the presence of 1-3 as third component. Following optimization, the power conversion efficiency (PCE) of the ternary OPV based on IN-DTPT-b20 (1) was significantly enhanced from 15.17 ± 0.28% (PM6:Y6) to 16.20 ± 0.26%. Tapping-mode atomic force microscopy (AFM) and grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis confirmed that incorporating IN-DTPT-b20 (1) into PM6:Y6 blend films effectively tailored the blend morphology, particularly by modulating the preferred orientation of Y6. The optimized morphology resulted in enhanced carrier mobility, reduced trap-assisted recombination, and efficient charge collection. These findings demonstrate the effectiveness of our NFA design strategy, further bolstered by the incorporation of IN-DTPT-b20 (1) as a guest acceptor, for achieving efficient OPV.