A new strategy for fabricating organic photovoltaic devices with stable D/A double-channel network to enhance performance using self-assembling all-conjugated diblock copolymer. (April 2015)

• Record Type: Journal Article
• Authors: Lee, Yi-Huan; Chen, Wei-Chih; Chiang, Chi-Ju; Kau, Kuo-Chang; Liou, Wei-Shin; Lee, Yu-Ping; Wang, Leeyih; Dai, Chi-An
• Is Part Of: Nano energy. Volume 13(2015:Apr.)
• Page Start: 103
• Page End: 116
• Publication Date: 2015-04
• Subjects: Conjugated polymer -- Polymer self-assembly -- Organic solar cells -- Diblock copolymer -- Electrics superhighway -- Long-term thermal stability; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2015.01.022
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: In this study, we demonstrate the cooperative self-assembly of [6, 6]-phenyl C61-butyric acid methyl ester (PCBM) and an all-conjugated poly(2, 5-dihexyloxy- p -phenylene)-b-poly(3-hexylthiophene) (PPP-P3HT) block copolymer to yield organic photovoltaic devices with enhanced solar cell performance and long-term stability. By a combination of TEM, GISAXS and GIWAXS structural investigations, it was found that a PPP-P3HT/PCBM hybrid film adopts a donor/acceptor (D/A) double-channel network (DCN) structure via simple spin-coating by self-organizing highly ordered and long-ranged crystalline P3HT nanofibrils as a hole-transporting channel, and the surrounding amorphous PPP domain with PCBM confined and dispersed within as the other electron-transporting channel. As a consequence of the structural development, the block copolymer hybrid solar cells could afford significant improvements in the charge transporting property and enhanced exciton separation, leading to a substantial improvement in the power conversion efficiency (PCE) of the resulting device. The photovoltaic devices with the DCN structure gave a high average PCE of 3.43% as compared to only 2.77% from a conventional P3HT/PCBM bulk heterojuction (BHJ) solar cell. Notably, the DCN solar cell showed significant improvements in thermal stability over the P3HT/PCBM BHJ solar cell in accelerated testing experiments. This enhancement is believed to be due to the nanoconfinement effect of the double-channel structure on the PCBM molecules, thereby averting PCBM aggregation problems typically occurring in BHJ devices. These results show promise for the practical usage of all-conjugated block copolymers with different main chain moieties towards the fabrication of organic photovoltaic devices with superior stability and competitive optoelectronic properties. Graphical abstract: Highlights: A new strategy was developed to create a donor/acceptor double-channel network (DCN) for efficient charge transport. The DCN structure was fabricated by the self-assembly of a structure-directing all-conjugated block copolymer and PCBM. The resulting DCN solar cells showed enhanced photovoltaic performance compared with conventional devices. In particular, the long-term thermal stability of the DCN devices was significantly improved.