Interplay of Intramolecular Noncovalent Coulomb Interactions for Semicrystalline Photovoltaic Polymers

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• 作者：Mohammad Afsar Uddin ; Tack Ho Lee ; Shuhao Xu ; Song Yi Park ; Taehyo Kim ; Seyeong Song ; Thanh Luan Nguyen ; Seo-jin Ko ; Sungu Hwang ; Jin Young Kim ; Han Young Woo
• 刊名：Chemistry of Materials
• 出版年：2015
• 出版时间：September 8, 2015
• 年：2015
• 卷：27
• 期：17
• 页码：5997-6007
• 全文大小：561K
• ISSN：1520-5002

文摘

Four different kinds of photovoltaic polymers were synthesized by controlling the intrachain noncovalent coulomb interactions through the incorporation of alkoxy- or alkylthio-substituted phenylene, 4,7-di(furan-2-yl)benzothiadiazole, and 4,7-di(thiophen-2-yl)benzothiadiazole as a building block. Fine modulation of the interplay of dipole鈥揹ipole, H-bond, and chalcogen鈥揷halcogen interactions (O路路路S, O路路路H, S路路路S, S路路路F, etc.) along the polymeric backbone influenced the chain planarity, interchain organization, film morphology, and electrical and photovoltaic properties significantly. By replacing the alkoxy substituents with alkylthio groups, the torsional angle increased (136鈥?68掳) due to the absence of an O路路路S attractive coulomb interaction (and/or increased S路路路S steric hindrance), enhancing the amorphous nature with hindered interchain packing. The alkoxy-substituted polymers exhibited nanofibrillar structures, showing strong interlamellar scattering peaks up to (300) with tight face-on 蟺鈥撓€ stacking in grazing incidence X-ray scattering. The measured carrier mobility of the alkoxy-containing polymers was 1鈥? orders of magnitude higher than that of the alkylthio-containing polymers. The incident-light-intensity-dependent photovoltaic characteristics clearly suggested efficient charge generation/extraction with less charge recombination for the alkoxy-containing semicrystalline polymers. The resulting photovoltaic energy conversion efficiency of the PPDT2FBT, PPDF2FBT, PPsDF2FBT, and PPsDT2FBT blended devices with PC₇₀BM was measured to be 8.28%, 5.63%, 5.12%, and 0.55%, respectively. This study suggests an important molecular design guideline for the further optimization of photovoltaic polymers and devices by finely controlling the interplay of the weak noncovalent coulomb interactions.