Conjugated polymer-functionalized graphite oxide sheets thin films for enhanced photovoltaic properties of polymer solar cells

• Published in: Journal of polymer science. Part B, Polymer physics Polymer physics, 2013-01, Vol.51 (2), p.137-148
• Main Authors: Lee, Rong-Ho, Huang, Jian-Lun, Chi, Chun-Han
• Format: Article
• Language: English
• Subjects: Application fields; Applied sciences; Blends; charge transport; conjugated polymers; electronic materials; Energy; Energy gaps (solid state); Exact sciences and technology; fullerenes; functionalization of polymers; Graphite; Homogeneity; Natural energy; Oxides; Photovoltaic cells; Photovoltaic conversion; Polymer blends; Polymer industry, paints, wood; polymers; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Technology of polymers; Thin films
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.23180

In this study, the maleimide‐thiophene copolymer‐functionalized graphite oxide sheets (PTM21‐GOS) and carbon nanotubes (PTM21‐CNT) were developed for polymer solar cell (PSC) applications. The grafting of PTM21‐OH onto the CNT and GO sheets was confirmed using FTIR spectroscopy. PTM21‐CNT and PTM21‐GOS exhibited excellent dispersal behavior in organic solvents. Better thermal stability was observed for PTM21‐CNT and PTM21‐GOS as compared with that for PTM21‐OH. In addition, the optical band gaps of PTM21‐GOS and PTM21‐CNT were lower than that of PTM21‐OH. We incorporated PTM21‐GOS and PTM21‐CNT individually into poly(3‐hexylthiophene) (P3HT)/[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) blends for use as photoconversion layers of PSCs. Good distributional homogeneity was observed for PTM21‐GOS or PTM21‐CNT in the P3HT/PCBM blend film. The UV–vis absorption peaks of the blend films red‐shifted slightly upon increasing the content of PTM21‐GOS or PTM21‐CNT. The band gap energies and LUMO/HOMO energy levels of the P3HT/PTM21‐GOS and P3HT/PTM21‐CNT blend films were slightly lower than those of the P3HT film. The conjugated polymer‐functionalized PTM21‐GOS and PTM21‐CNT behaved as efficient electron acceptors and as charge‐transport assisters when incorporated into the photoactive layers of the PSCs. PV performance of the PSCs was enhanced after incorporating PTM21‐GOS or PTM21‐CNT in the P3HT/PCBM blend. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 Nanocarbon materials such as carbon nanotubes and graphite oxide sheets (GOSs) have large contact areas, high‐aspect ratios, and good electrical conductivities. This means that the electro‐optical properties of organic optoelectronic devices are often improved by incorporating them. Here, conjugated polymer‐functionalized GOSs efficiently assist charge transport in polymer solar cells, enhancing charge transfer from the polymer units to the cathode. The polymer/fullerene/GOS films are structurally, thermally, optically, and electrochemically characterized, in addition to being tested in solar cells.