Synthesis and application of H-Bonded cross-linking polymers containing a conjugated pyridyl H-Acceptor side-chain polymer and various carbazole-based H-Donor dyes bearing symmetrical cyanoacrylic acids for organic solar cells Duryodhan Sahu a , Harihara Padhy a , Dhananjaya Patra a , Dhananjay Kekuda b , Chih-Wei Chu b, c , I-Hung Chiang a , Hong-Cheu Lin a, * a Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, Taiwan, ROC b Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan, ROC c Department of Photonics, National Chiao Tung University, Hsinchu, Taiwan, ROC article info Article history: Received 12 August 2010 Received in revised form 4 October 2010 Accepted 10 October 2010 Available online 26 October 2010 Keywords: H-bonded polymer network Solar cell Self-assembly abstract A series of novel hydrogen-bonded (H-bonded) cross-linking polymers were generated by complexing various proton-donor (H-donor) solar cell dyes containing 3,6- and 2,7-functionalized electron-donating carbazole cores bearing symmetrical thiophene linkers and cyanoacrylic acid termini with a proton- acceptor (H-acceptor) side-chain homopolymer carrying pyridyl pendants (with 1/2 M ratio of H-donor/ H-acceptor). The supramolecular H-bonded structures between H-donor dyes and the H-acceptor side- chain polymer were confirmed by FTIR measurements. The effects of the supramolecular architecture on optical, electrochemical, and organic photovoltaic (OPV) properties were investigated. From DFT (density functional theory) calculations, the optimized geometries of organic dyes reflected that the carbazole cores of H-donor dyes were coplanar with the conjugated thiophenes and cyanoacrylic acids, which is essential for strong conjugations across the donor-acceptor units in D1eD4 dyes. Under 100 mW/cm 2 of AM 1.5 white-light illumination, bulk heterojunction (BHJ) OPV cell devices containing an active layer of H-bonded polymers (PDFTP/D1eD4) as an electron donor blended with [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) as an electron acceptor in a weight ratio of 1:1 were explored. From the preliminary investigations, the OPV device containing 1:1 weight ratio of H-bonded polymer PDFTP/D2 and PCBM showed the best power conversion efficiency (PCE) value of 0.31% with a short-circuit current (J sc ) of 1.9 mA/cm 2 , an open-circuit voltage (V oc ) of 0.55 V, and a fill factor (FF) of 29%, which has a higher PCE value than the corresponding H-donor D2 dye (PCE ¼ 0.15%) or H-acceptor PDFTP homopolymer (PCE ¼ 0.02%) blended with PCBM in 1:1 weight ratio. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction In order to overcome the growing global energy needs, extensive researches on environment friendly and renewable sources of ener- gies have been made during the past decade [1,2]. As an ecologically sustainable and renewable source of energies, solar energy led to a greater attention for the scientists to develop solar energy conver- sion devices [3,4]. Since then, p-conjugated oligomers and polymers were applied as advanced materials for the development of organic photovoltaic (OPV) devices for future applications [5,6]. After the breakthrough work of Heeger and coworkers in 1995 [7], bulk het- erojunction (BHJ) solar cells became a low-cost, flexible, and large- area processible [8,9] alternatives to silicon-based solar cells, though their efficiencies are not comparable to those of silicon-based tech- nologies. In fact, different solar cell architectures have been devel- oped, including dye sensitized solar cells [10e12], donor-acceptor BHJs of polymer blends [13e19] and block copolymers [20], supra- molecular ensemble of small molecule/small molecule [21] etc. However, the interests on oligomers with easy purification processes and lack of problems in molecular weight distributions etc. are generally auxiliary to their polymer analogues due to the better solvent processabilities and film morphologies in photovoltaic cells [22]. Therefore, in order to get the advantages of both oligomeric and polymeric properties, an attractive approach would be the well- defined supramolecular architectures of p-conjugated oligomers with the processabilities of polymers [23]. Since conjugated polymers with electron donor-acceptor (D-A) architectures had proved as the highly efficient solar cell polymers * Corresponding author. Tel.: þ8863 5712121x55305; fax: þ8863 5724727. E-mail address: linhc@cc.nctu.edu.tw (H.-C. Lin). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2010.10.018 Polymer 51 (2010) 6182e6192