The role of local potential minima on charge transport in thin organic semiconductor layers |
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| Affiliation: | 1. Department of Physics, Ajou University, Suwon 443-749, South Korea;2. Department of Energy Systems Research, Ajou University, Suwon 443-749, South Korea;1. Department of Chemistry, Fu Jen Catholic University, New Taipei City 24205, Taiwan;2. Department of Opto-Electronic Engineering, National Dong Hwa University, Hualien 97401, Taiwan;1. Department of Materials Science and Engineering, University of Florida, Gainesville, FL, 32611, United States;2. Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC, 27607, United States;1. Wuhan University, 8 East Lake South Road, Wuchang Dist., Wuhan, 430072, China;2. International and Inter University Centre for Nanoscience and Nanotechnology, School of Chemical Sciences, Mahatma Gandhi University, Priyadarshini Hills P. O. Kottayam, Kerala, 686560, India;3. Liquid Crystal Research Laboratory (LCRL), Bannari Amman Institute of Technology, Sathyamangalam, 638 401, India;1. Key Laboratory of Interface Science and Engineering in Advanced Materials (Taiyuan University of Technology), Ministry of Education, Taiyuan, 030024, China;2. Research Center of Advanced Materials Science and Technology, Taiyuan University of Technology, Taiyuan, 030024, China;3. Department of Physics, Institute of Advanced Materials, and Institute of Research and Continuing Education (Shenzhen), Hong Kong Baptist University, Kowloon Tong, NT, Hong Kong, China;4. School of Physical Science and Electronics, Shanxi Datong University, Datong, 037009, China;5. School of Chemistry and Chemical Engineering, Shanxi University, Taiyuan, 030006, China |
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| Abstract: | We have performed a systematic study of dependence of time-resolved photocurrent on the point of charge excitation within the organic semiconductor channel formed by two coplanar metal electrodes. The results confirm that spatial variation of electric field between the electrodes crucially determines transport of photogenerated charge carriers through the organic layer. Time-of-flight measurements of photocurrent demonstrate that the transit time of photogenerated charge carrier packets drifting between the two electrodes decreases with increasing travelling distance. Such counterintuitive result cannot be reconciled with the spatial distribution of electric field between coplanar electrodes, alone. It is also in contrast to expected role of space-charge screening of external electric field. Supported by Monte Carlo simulations of hopping transport in disordered organic semiconductor layer, we submit that the space-charge screens the external electric field and captures slower charge carriers from the photogenerated charge carrier packet. The remaining faster carriers, exhibit velocity distribution with significantly higher mean value and shorter transit time. |
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| Keywords: | Charge transport Organic semiconductors Time of flight Mobility Traps |
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