Synthesis of selenophene substituted benzodithiophene and fluorinated benzothiadiazole based conjugated polymers for organic solar cell applications

• Published in: Electrochimica acta 2021-12, Vol.398, p.139298, Article 139298
• Main Authors: Aslan, Sultan Taskaya, Cevher, Duygu, Bolayır, Eda, Hizalan Ozsoy, Gonul, Arslan Udum, Yasemin, Yıldırım, Erol, Toppare, Levent, Cirpan, Ali
• Format: Article
• Language: English
• Subjects: Atomic properties; Benzodithiophene; Benzothiadiazole; Copolymers; Density functional theory; Electronic structure; Energy levels; Fluorine; Fluorine substitution; Optical properties; Organic solar cell; Photovoltaic cells; Polycondensation reactions; Polymers; Power conversion efficiency; Solar cells; Substitution reactions
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2021.139298

•Polymers with selenophene substituted benzodithiophene and benzothiadiazole was synthesized.•BHJ solar cells fabricated with ITO/PEDOT:PSS/Polymer:PC71BM/LiF/Al configuration.•The effect of the number of f atoms on benzothiadiazole acceptor was investigated.•The DIO addition into the blend increased the efficiency of the solar cells.•The solar cell reached the highest efficiency up to 2.63% for PBDTSe-FFBT polymer. A series of alternating conjugated copolymers which contain selenophene modified benzodithiophene and fluorine bearing benzothiadiazole have been synthesized via Stille polycondensation reaction to investigate the effect of the number of fluorine atoms substituted to the benzothiadiazole. Three different polymers, PBDTSe-BT, PBDTSe-FBT and PBDTSe-FFBT, were reported and their electrochemical, spectroelectrochemical, and photovoltaic behaviors were examined. Density functional theory calculations were performed on model tetramer structures to shed light on how substituting the fluorine atom to the acceptor building block affects the structural, electronic and optical properties of the polymers. The results of computational studies were compared with experimental studies. The structure adjustment accomplished by fluorine substitution on the benzothiadiazole moiety reveals an influence on the electronic structure of polymers with a more negative HOMO energy level. A high VOC for the resulting photovoltaic device was examined for PBDTSe-FFBT. Difluorinated polymer PBDTSe-FFBT:PC71BM organic solar cell exhibited the highest photovoltaic performance of 2.63% with JSC of 7.24 mA cm-2, VOC of 0.72 V and FF of 50.6%. PBDTSe-BT:PC71BM revealed the best PCE as 2.39%, and the device reached the highest efficiency up to 1.68% for PBDTSe-FBT:PC71BM. [Display omitted]