Polymer solar cell by blade coating Yu-Han Chang a , Shin-Rong Tseng a , Chun-Yu Chen a , Hsin-Fei Meng a, * , En-Chen Chen b , Sheng-Fu Horng b , Chian-Shu Hsu c a Institute of Physics, National Chiao Tung University, Hsinchu 300, Taiwan, Republic of China b Department of Electrical Engineering, National Tsing Hua University, Hsinchu 300, Taiwan, Republic of China c Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan, Republic of China article info Article history: Received 3 November 2008 Received in revised form 11 February 2009 Accepted 4 March 2009 Available online 13 March 2009 PACS: 72.80.Le 72.10.d 72.20.Ht Keywords: Organic photovoltaic Polymer solar cell Bulk hetero-junction Blade coating abstract Polymer bulk hetero-junction solar cells of poly(3-hexylthiophene) (P3HT) donor and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) acceptor are fabricated by blade coat- ing in toluene solution. Desired donor–acceptor self-organization is achieved without the slow drying process and high boiling point solvent. Power conversion efficiency is 3.8%, much higher than the 2.6% obtained by spin coating in toluene solution. The blade coating method has nearly 100% material usage and can be integrated in the roll-to-roll process with high throughput production. Ó 2009 Elsevier B.V. All rights reserved. Recently conjugated polymer solar cells have attracted great interests due to their unique properties such as easy solution process for large-area, light weight, and mechani- cal flexibility. The polymer bulk hetero-junction cells have interpenetrating networks of electron donors and accep- tors, resulting in an efficient exciton dissociation and high photo-currents with the power conversion efficiency (PCE) about 5% [1,2]. Although the efficiency is not as high as that of inorganic solar cells, the potential of low-cost and roll- to-roll process on flexible substrates makes the polymer solar cells attractive as the solution to the serious energy challenges. However, to date most of the efficient polymer solar cells are made by spin coating, which causes serious material waste and raises the cost dramatically. In addi- tion, the spin coating process is not easy to scale up to very large sizes up to meters and is incompatible with the roll- to-roll process for high throughput production. Further- more one major problem of the spin coated polymer solar cell is that a very toxic high boiling point organic solvent like dichlorobenzene (180.5 °C) or chlorobenzene (131 °C) is necessary for high efficiency. The high boiling point al- lows a slow drying process where the donor and acceptor molecules self-assemble into an interpenetrating network [1]. The high toxicity of dichlorobenzene and chloroben- zene makes the mass production environmentally un- friendly, and the slow drying process delays the production throughput. Although there have been re- searches on fabrication processes, including ink-jet print- ing [3], screen printing [4], spray coating [5], and blade coating[6], the development of alternative solution coating methods compatible with the low-cost and environmen- tally friendly mass production remains a crucial problem [7]. Since there is no necessary for organic layers to be 1566-1199/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.orgel.2009.03.001 * Corresponding author. E-mail address: meng@mail.nctu.edu.tw (H.-F. Meng). Organic Electronics 10 (2009) 741–746 Contents lists available at ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel