Carrier Dynamics of p-n Heterojunction Organic Photovoltaic Cells Analyzed by a Novel Graphic Representation of Impedance Spectroscopy
Carrier Dynamics of p-n Heterojunction Organic Photovoltaic Cells Analyzed by a Novel Graphic Representation of Impedance Spectroscopy作者机构：Interdisciplinary Graduate School of Science and Engineering Tokyo Institute of Technology Yokohama Japan Advanced Technology Research Laboratories Idemitsu Kosan Co. Ltd. Sodegaura Japan Research Center for Photovoltaic Technologies AIST Tsukuba Japan
出 版 物：《Advances in Materials Physics and Chemistry》 (材料物理与化学进展（英文）)
年 卷 期：2015年第5卷第1期
页 面：1-9页
学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学]
主 题：Organic Photovoltaic Cells Impedance Spectroscopy Modulus Analysis
摘 要：The carrier dynamics in organic photovoltaic (OPV) cells were investigated by impedance spectroscopy. We introduced a novel impedance spectrum representation called dynamic modulus plot (DMP), which allowed us to observe the layer-to-layer carrier injection behavior graphically. In this work, the impedance responses were characterized in the N,N’-diphenyl-N,N’-di-m-tolyl- 4,4’-diaminobiphenyl (TPD)/C60 p-n heterostructured OPV cells against applied voltages. The dependence of impedance responses on the layer thickness revealed a constant internal electric field that disturbed the carrier transport within the OPV cells. We applied this technique to new donor materials, in which thiophene units were inserted to the center of TPD. By increasing the number of thiophene units in TPD the fill-factor (FF) improved from 33% to 59%, which increased the power conversion efficiency (PCE). Based on the DMP analysis, we assigned the improvement in device performance to the reduction of the internal electric field.
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