Effect of thiophene, 3-hexylthiophene, selenophene, and Thieno[3,2-b] thiophene spacers on OPV device performance of novel 2,1,3-benzothiadiazole based alternating copolymers

Four novel alternating copolymers bearing 5-fluoro-6-((2-octyldodecyl)oxy)benzo[c][1,2,5]thiadiazole as a strong acceptor unit and 9,9-dioctylfluorene as a strong donor unit with bridging units namely, thienothiophene, selenophene, 3-hexylthiophene, and thiophene were designed and synthesized. The polymers were characterized via 1H NMR spectroscopy, and weight average molecular weights were reported via gel permeation chromatography (GPC). For synthesized novel polymers, the bulk heterojunction solar cells were constructed. Besides, the effects of bridging units on electronic, optical, photovoltaic, and morphological properties were investigated. Among the polymers, the thienothiophene containing polymer P1 exhibited the highest PCE as 4.25% under the illumination of AM 1.5 G with 100 mW/cm2.

Automated summary

Four novel alternating copolymers were designed and synthesized, with thienothiophene, selenophene, 3-hexylthiophene, and thiophene as bridging units. These polymers were characterized and used in bulk heterojunction solar cells, with the thienothiophene-containing polymer P1 showing the highest power conversion efficiency of 4.25%.