Backbone Engineering with Fluoroarene to Mitigate Morphological Disorder for High-Performance Polymer Solar Cells AITranslate

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DOI：https://doi.org/10.1021/acsapm.1c00989

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Three random terpolymers were synthesized by subtle incorporation of fluoroarenes as the third monomer into the popular PTB7-Th backbone and utilized for photovoltaic applications. By substituting 5% of 3-fluorothieno[3,4-b]thiophene-2-carboxylate in the PTB7-Th backbone using monomers such as 2,5-difluorobenzene, 2,3-difluorobenzene, and 2,3,5,6-tetrafluorobenzene, random terpolymers M1, M2, and M3 were synthesized, respectively. The presence of fluorinated monomers deepened the highest occupied molecular orbital (HOMO) energy level of terpolymers, which substantially enhanced the open circuit voltage (VOC) of polymer solar cells (PSCs). The power conversion efficiency (PCE) for M1- and M2-based PSCs reached up to 9.48 and 8.80% from 8.19% for the PTB7-Th:PC71BM blend. However, M3-based blend exhibited an inferior PCE of 8.13% majorly due to its weaker absorption in the higher-wavelength region and lower carrier mobility. The M1 polymer also exhibited an enhanced PCE of 9.01% compared to 7.68% for PTB7-Th with ITIC, a non-fullerene acceptor. Moreover, the fluoroarenes induced intra/intermolecular non-covalent interactions in blend films. These interactions acted as a conformational lock to tune the morphology that also improved the phase domain stability. M1:PC71BM-based PSC displayed superior capability to sustain under ambient conditions and it retained 82% of its initial PCE after 1000 h of ambient exposure in comparison to 51% of the PTB7-Th blend under a relative humidity of 45 ± 5%. This generic approach can be utilized in finely modulating the property of photovoltaic materials to enhance the performance along with the stability of PSCs.