The open circuit voltage of photovoltaic devices can often be improved by decreasing the highest occupied molecular orbital (HOMO) energy level,through the fluorination of small molecule donors, which is beneficial to obtaining higher photoelectric conversion efficiency (PCE). In this work, a new conjugated linker containing 3',4'-difluoro-3,3"-dioctyltrithiophene unit was designed and synthesized. Through the Stille coupling, Knoevenegal condensation reactions and some other reactions, a new small molecule electron donor (namely BDT4F-RO) that with benzodithiophene substituted side chain as the core, fluoro tribithiophene as the conjugate bridge and rhodanine as the end group was synthesized. The molecular structure and properties were preliminarily characterized by NMR spectroscopy (1H NMR, 13C NMR and 19F NMR), UV-Vis spectroscopy, cyclic voltammetry (CV) and thermogravimetric analysis (TGA), respectively. The results show that BDT4F-RO exhibits strong absorption in 300—700 nm area in thin film, and the absorption onset is located at 690 nm. Compared with BDT-RO, the analogue without fluorine atoms, BDT4F-RO has a deeper HOMO energy level, which is beneficial to a higher open-circuit voltage(0. 95 V) of the fabricated photovoltaic device. However, the photo-electron conversion efficiency of BDT4F-RO is generally inferior to that of BDT-RO, and this can be attributed to lo-wer miscibility of BDT4F-RO:IDIC blend that caused by fluorination. © 2022 Cailiao Daobaoshe/ Materials Review. All rights reserved.
