Investigation of Charge Carrier Behavior in High Performance Ternary Blend Polymer Solar Cells |
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| Authors: | Tack Ho Lee Mohammad Afsar Uddin Chengmei Zhong Seo‐Jin Ko Bright Walker Taehyo Kim Yung Jin Yoon Song Yi Park Alan J Heeger Han Young Woo Jin Young Kim |
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| Institution: | 1. Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea;2. Department of Chemistry, Korea University, Seoul, Republic of Korea;3. Department of Cogno‐Mechatronics Engineering, Pusan National University, Miryang, Republic of Korea;4. Center for Polymers and Organic Solids, University of California Santa Barbara, Santa Barbara, CA, USA;5. State Key Laboratory of Luminescent Materials and Devices, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, China |
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| Abstract: | This study demonstrates high‐performance, ternary‐blend polymer solar cells by modifying a binary blend bulk heterojunction (PPDT2FBT:PC71BM) with the addition of a ternary component, PPDT2CNBT. PPDT2CNBT is designed to have complementary absorption and deeper frontier energy levels compared to PPDT2FBT, while being based on the same polymeric backbone. A power conversion efficiency of 9.46% is achieved via improvements in both short‐circuit current density (JSC) and open‐circuit voltage (VOC). Interestingly, the VOC increases with increasing the PPDT2CNBT content in ternary blends. In‐depth studies using ultraviolet photoelectron spectroscopy and transient absorption spectroscopy indicate that the two polymers are not electronically homogeneous and function as discrete light harvesting species. The structural similarity between PPDT2CNBT and PPDT2FBT allows the merits of a ternary system to be fully utilized to enhance both JSC and VOC without detriment to fill‐factor via minimized disruption of semi‐crystalline morphology of binary PPDT2FBT:PC71BM blend. Further, by careful analysis, charge carrier transport in this ternary blend is clearly verified to follow parallel‐like behavior. |
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| Keywords: | alloy‐like polymers parallel‐like bulk heterojunctions polymer solar cells ternary blend systems transient absorption spectroscopy |
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