Photophysical, electrochemical and photovoltaic properties of thiophene-containing arylene-ethynylene/arylene-vinylene polymers

摘要

This work reports the properties of two types of thiophene-containing poly(arylene-ethynylene)-alt-poly(arylene-vinylene)s polymers, whose repeating units (-Ph-C≡C-Th-CH=CH-Ph-CH=CH-)_n, 1, and (-Th-C≡C-Ph-C≡C-Th-CH=CH-Ph-CH=CH-)_n, 2, consist respectively of a 1:2 and a 2 :2 ratio of -C≡C-/-CH=CH- moieties. Although similar electrochemical data (HOMO: - 5.43 eV, LUMO: ～- 3.15 eV, E_g~(ec)=2.28 eV) as well as identical thin film absorption behaviour (λ_a=501 nm, E_g~(opt)=2.10 eV) were obtained for both types of materials, significant differences in their thin film photoluminescence behaviour and photovoltaic properties were observed. While polymer 1 shows a fluorescence maximum at λ_e=568 nm (with a fluorescence quantum yield of Φ_f=7%), a total fluorescence quenching was observed in 2. Solar cells (set up: ITO/PEDOT:PSS/active layer/LiF/Al; active layer consisting of 1 or 2 as donor and PCBM as acceptor in a 1:3 ratio by weight) designed from 1 (best cell: Ⅴ_(OC)=900 mV, Ⅰ_(SC)=2.51 mA·cm~(-2), FF = 53.7%, η_(AM1.5)= 1.21%) show far better photovoltaic performance than those from 2 (best cell: Ⅴ_(OC) = 500 mV, Ⅰ_(SC)=1.44 mA·cm~(-2), FF=37.1%, η_(AM1.5)=0.27%).