Transient space-charge-perturbed currents in organic materials: A Monte Carlo study |
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| Affiliation: | 1. Department of Materials Science and Engineering, National Tsing Hua University, Hsin Chu, Taiwan;2. Department of Chemistry, National Tsing Hua University, Hsin Chu, Taiwan;3. Institute of Physics, National Chiao Tung University, Hsin Chu, Taiwan;4. Material and Chemical Research Laboratories, Industrial Technology Research Institute (ITRI), Hsin Chu, Taiwan;1. Information and Communications Technologies Portfolio, National Research Council of Canada, Ottawa, ON K1A 0R6, Canada;2. Département de Chimie, Université Laval, Québec City, QC G1V 0A6, Canada;1. Congenital Heart Center, Shands Children''s Hospital, University of Florida, Gainsville, Fla;2. Section of Critical Care and Congenital Heart Surgery, Department of Pediatrics, Baylor College of Medicine, Houston, Tex;3. Section of Critical Care Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, Tex;4. Section of Cardiology, Department of Pediatrics, Baylor College of Medicine, Houston, Tex;5. Department of Pediatrics, Baylor College of Medicine, Houston, Tex;6. Section of Congenital Heart Surgery, Department of Surgery, Baylor College of Medicine, Houston, Tex;7. Section of Critical Care, Texas Section of Children''s Hospital, Houston, Tex |
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| Abstract: | The transient current holds rich information about carrier transport and is used to derive charge mobility in the time-of-flight (TOF) measurement. Because carriers have finite charge, all transient currents are space-charge-perturbed (SCP). Previous theories of transient SCP currents are derived by neglecting diffusion and assuming a constant mobility, which is unfit for organic materials because of the hopping behavior of carriers. Due to the lack of knowledge, we do not fully understand the results from TOF experiments, which hinders the understanding of the charge transport mechanisms. Here, we perform Monte Carlo simulations of multi-particle carrier movement to study the transient SCP currents in organic materials. Coulomb interactions are calculated, and it is assumed that multiple carriers cannot occupy the same site simultaneously. Our results show that space-charge perturbation has two opposite effects on charge transport. In most cases, the net result is slower carrier movement, which suggests that TOF measurements under SCP conditions underestimate the charge mobility of organic materials. |
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| Keywords: | Charge transport Charge mobility Carrier propagation Time-of-flight Carrier density |
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