中国物理B ›› 2018, Vol. 27 ›› Issue (6): 67202-067202.doi: 10.1088/1674-1056/27/6/067202

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

How to characterize capacitance of organic optoelectronic devices accurately

Hao-Miao Yu(于浩淼), Yun He(何鋆)   

  1. 1 Key Laboratory of Luminescence and Optical Information, Ministry of Education, School of Science, Beijing Jiaotong University, Beijing 100044, China;
    2 National Key Laboratory of Science and Technology on Space Microwave, China Academy of Space Technology(Xi'an), Xi'an 710100, China
  • 收稿日期:2017-12-26 修回日期:2018-03-12 出版日期:2018-06-05 发布日期:2018-06-05
  • 通讯作者: Hao-Miao Yu, Yun He E-mail:yuhaomiao@bjtu.edu.cn;081019028@fudan.edu.cn
  • 基金资助:
    Project supported by the Fundamental Research Funds for the Central Universities,China

How to characterize capacitance of organic optoelectronic devices accurately

Hao-Miao Yu(于浩淼)1, Yun He(何鋆)2   

  1. 1 Key Laboratory of Luminescence and Optical Information, Ministry of Education, School of Science, Beijing Jiaotong University, Beijing 100044, China;
    2 National Key Laboratory of Science and Technology on Space Microwave, China Academy of Space Technology(Xi'an), Xi'an 710100, China
  • Received:2017-12-26 Revised:2018-03-12 Online:2018-06-05 Published:2018-06-05
  • Contact: Hao-Miao Yu, Yun He E-mail:yuhaomiao@bjtu.edu.cn;081019028@fudan.edu.cn
  • Supported by:
    Project supported by the Fundamental Research Funds for the Central Universities,China

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摘要： The selection of circuit model (i.e., parallel or series model) is critical when using a capacitance-frequency and capacitance-voltage technique to probe properties of organic materials and physical processes of organic optoelectronic devices. In the present work, capacitances of ITO/Alq3/Al and ITO/CuPc/Al are characterized by series and parallel model, respectively. It is found that the large series resistance comes from the ITO electrode and results in the inapplicability of the parallel model to measuring the capacitances of organic devices at high frequencies. An equivalent circuit model with consideration of the parasitical inductance of cables is constructed to derive the capacitance, and actual capacitance-frequency spectra of Alq3 and CuPc devices are obtained. Further investigation of temperature-dependent capacitance-frequency and capacitance-voltage characteristics indicates that CuPc and Al form the Schottky contact, the density and ionization energy of impurities in CuPc are obtained. Moreover, more practical guidelines for accurate capacitance measurement are introduced instead of the impedance magnitude, which will be very helpful for the organic community to investigate capacitance-related characteristics when dealing with various organic optoelectronic devices.

关键词: organic semiconductor, capacitance characterization, Schottky contact, ionization energy

Abstract: The selection of circuit model (i.e., parallel or series model) is critical when using a capacitance-frequency and capacitance-voltage technique to probe properties of organic materials and physical processes of organic optoelectronic devices. In the present work, capacitances of ITO/Alq3/Al and ITO/CuPc/Al are characterized by series and parallel model, respectively. It is found that the large series resistance comes from the ITO electrode and results in the inapplicability of the parallel model to measuring the capacitances of organic devices at high frequencies. An equivalent circuit model with consideration of the parasitical inductance of cables is constructed to derive the capacitance, and actual capacitance-frequency spectra of Alq3 and CuPc devices are obtained. Further investigation of temperature-dependent capacitance-frequency and capacitance-voltage characteristics indicates that CuPc and Al form the Schottky contact, the density and ionization energy of impurities in CuPc are obtained. Moreover, more practical guidelines for accurate capacitance measurement are introduced instead of the impedance magnitude, which will be very helpful for the organic community to investigate capacitance-related characteristics when dealing with various organic optoelectronic devices.

Key words: organic semiconductor, capacitance characterization, Schottky contact, ionization energy

中图分类号:  (Charge carriers: generation, recombination, lifetime, and trapping)

  • 72.20.Jv
72.80.Le (Polymers; organic compounds (including organic semiconductors)) 73.30.+y (Surface double layers, Schottky barriers, and work functions) 73.61.Ph (Polymers; organic compounds)