Enhancement of photovoltaic properties in supramolecular polymer networks featuring a solar cell main-chain polymer H-bonded with conjugated cross-linkers

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• 作者：Dhananjaya Patra^a ; Mohan Ramesh^a ; Duryodhan Sahu^a ; Harihara Padhy^a ; Chih-Wei Chu^b ; ^c ; ^{gchu@gate.sinica.edu.tw} ; Kung-Hwa Wei^a ; Hong-Cheu Lin^a ; ^{linhc@cc.nctu.edu.tw}
• 关键词：H-bonded cross-linker ; Supramolecule ; Polymer network
• 刊名：Polymer
• 出版年：2012
• 期刊代码：83_00323861
• 类别：ms
• 出版时间：9 March, 2012
• 卷：53
• 期：6
• 页码：1219-1228
• 文件大小：1137 K

摘要

Stille polymerization was employed to synthesize a low-band-gap (LBG) conjugated main-chain polymer PBTH consisting of bithiazole, dithieno[3,2-b:2鈥?3鈥?d]pyrroles (DTP), and pendent melamine derivatives. Novel supramolecular polymer networks PBTH/C and PBTH/F were developed by mixing proper molar amounts of polymer PBTH (containing melamine pendants) to be hydrogen-bonded (H-bonded) with complementary uracil-based conjugated cross-linkers C and F (i.e., containing two symmetrical uracil moieties connected with carbazole and fluorene units through triple bonds). The formation of multiple H-bonds between polymer PBTH and cross-linkers C or F was confirmed by FT-IR measurements. In contrast to polymer PBTH, the supramolecular design with multiple H-bonds can enhance the photovoltaic properties of polymer solar cell (PSC) devices containing H-bonded polymer networks PBTH/C and PBTH/F by tuning their light harvesting capabilities, HOMO energy levels, and crystallinities. Initially, the power conversion efficiency (PCE) values of PSC devices containing supramolecular polymer networks PBTH/C and PBTH/F as electron donors and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₀BM) as an electron acceptor (polymer:PC₇₀BM聽=聽1:1 w/w) are found to be 0.97 and 0.68%, respectively, in contrast to 0.52%for polymer PBTH. The highest PCE value of 1.56%with a short-circuit current densities (J_sc) value of 7.16聽mA/cm², a open circuit voltages (V_oc) value of 0.60聽V, and a fill factor (FF) of 0.36 was further optimized in the PSC device containing a supramolecular polymer network PBTH/C as polymer:PC₇₀BM聽=聽1:2 w/w. These results indicate that supramolecular design is an effective route towards better photovoltaic properties of V_oc, J_sc, and PCE values in polymer solar cells.