Syntheses and optical, electrochemical, and photovoltaic properties of polymers with 6-(2-thienyl)-4H-thieno[2,3-b]indole with a variety of electron-deficient units

摘要

Conjugated polymers were synthesized and used for polymer solar cells with new electron-rich units, 6-(2-thienyl)-4H-thieno[2,3-b]indole (2-TTI). 2-TTI was coupled with electron-pulling units, including benzothiadiazole and benzimidazole derivatives, to provide push-pull types of conjugated polymers (poly(8-(heptadecan-9-yl)-6-(thiophen-2-yl)-8H-thieno[2,3-b]indole)-alt-(2-methyl-5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)-2-(trifluoromethyl)-2H-benzimidazole) (PTTIDOCF3), poly(8-(heptadecan-9-yl)-6-(thiophen-2-yl)-8H-thieno[2,3-b]indole)-alt-(5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)-2,1,3-benzothiadiazole) (PTTIDOBT), poly(8-(heptadecan-9-yl)-6-(thiophen-2-yl)-8H-thieno[2,3-b]indole)-alt-(2,2-dimethyl-4,7-di(thiophen-2-yl)-2H-benzimidazole) (PTTIMBI), and poly(8-(heptadecan-9-yl)-6-(thiophen-2-yl)-8H-thieno[2,3-b]indole)-alt-(2,2-dimethyl-5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)-2H-benzimidazole) (PTTIDOMBI)). The synthesized conjugated polymers provided deep highest occupied molecular orbital energy levels for higher open-circuit voltages (V-OC). The device composed of PTTIDOMBI and [6,6]-Phenyl C-71 butyric acid methyl ester PC71BM (1:2) with chloronaphthalene additive showed a V-OC of 0.72 V, a short-circuit current (J(SC)) of 9.16 mA/cm(2), and a fill factor of 0.43; this gave a power conversion efficiency (PCE) of 2.84%. The PTTIDOMBI provided better morphology for enhanced charge transport, and this led to the higher J(SC) and PCE of the organic solar cells. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47624.