Additive-free organic solar cells with enhanced efficiency enabled by unidirectional printing flow of high shear rate |
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| Affiliation: | 1. School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China;2. MIIT Key Laboratory of Advanced Solid Laser, Nanjing University of Science and Technology, Nanjing 210094, PR China;3. School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China;4. Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan;1. Institute of Physics and Electronic Information, Yunnan Normal University, Kunming, 650500, China;2. Yunnan Key Laboratory of Optoelectronic Information Technology, Kunming, 650500, China;3. Key Laboratory of Advanced Technique & Preparation for Renewable Energy Materials, Ministry of Education, Yunnan Normal University, Kunming, 650500, China;1. Institute of Physics and Electronic Information, Yunnan Normal University, Kunming, 650500, China;2. Yunnan Key Laboratory of Optoelectronic Information Technology, Kunming, 650500, China;3. Key Laboratory of Advanced Technique & Preparation for Renewable Energy Materials, Ministry of Education, Yunnan Normal University, Kunming, 650500, China |
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| Abstract: | High-performance OSCs prepared by scalable techniques without additives are highly desirable because residual additives may cause gradual deterioration of the photoactive-layer morphology and device performance. Printing flows with high shear rate have the potential to replace additives by inducing higher degree of ordered stacking and crystallinity of organic molecules, as well as favorable phase separation. Here, PTQ10:Y6 organic solar cells (OSCs) without any additives were fabricated by a scalable and robust processing approach termed as soft porous blade printing (SPBP). The fluid flow and drying process of the wet films made by SPBP, blade coating and spin coating are visualized by high speed imaging, which reveals that the blade coating and SPBP introduce unidirectional flow while the wet film interference pattern of spin coating is irregular and random. The simplified flow model of SPBP suggests that the shear rate could be as high as ~1000 s−1. The additive-free SPBP produces photoactive-layer with adequate morphology, which could be attributed to three intrinsic properties of SPBP: very high shear rate, flow assisted crystallizations induced by microstructures of the soft porous blade, and numerous nucleation sites generated as the liquid contact line follows the motion of the blade. The additive-free SPBP device demonstrates weaker charge recombination, higher and more balanced charge transport, and consequently better device performance than the spin-coated and blade-coated devices with 0.25 vol% 1,8-diioctane (DIO). SPBP achieved power conversion efficiency (PCE) of 16.45%, which is higher than those of spin-coated and blade-coated counterparts doped with DIO. |
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| Keywords: | Organic solar cells Shear rate Additive free Soft porous blade printing |
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