Electronic states of Ca/PC61BM: Mechanism of low work function metal as interfacial material

Ying-Ying Du; Guang-Hua Chen; Wen-Jie Li; Xin-Yuan Bai; De-Qu Lin; Huanxin Ju; Shanwei Hu; Qian Xu; Yan Wang; Xiong Li; Junfa Zhu; Hong-Nian Li

doi:10.1063/1.5017181

AIP Advances (Mar 2018)

Electronic states of Ca/PC61BM: Mechanism of low work function metal as interfacial material

Ying-Ying Du,
Guang-Hua Chen,
Wen-Jie Li,
Xin-Yuan Bai,
De-Qu Lin,
Huanxin Ju,
Shanwei Hu,
Qian Xu,
Yan Wang,
Xiong Li,
Junfa Zhu,
Hong-Nian Li

Affiliations

Ying-Ying Du: Department of Physics, Zhejiang University, Hangzhou 310027, China
Guang-Hua Chen: Department of Physics, Zhejiang University, Hangzhou 310027, China
Wen-Jie Li: Department of Physics, Zhejiang University, Hangzhou 310027, China
Xin-Yuan Bai: Department of Physics, Zhejiang University, Hangzhou 310027, China
De-Qu Lin: Department of Physics, Zhejiang University, Hangzhou 310027, China
Huanxin Ju: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Shanwei Hu: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Qian Xu: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Yan Wang: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Xiong Li: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Junfa Zhu: National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Hong-Nian Li: Department of Physics, Zhejiang University, Hangzhou 310027, China

DOI: https://doi.org/10.1063/1.5017181
Journal volume & issue: Vol. 8, no. 3
pp. 035015 – 035015-7

Abstract

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We have studied the electronic states at Ca/PC61BM interface using photoemission spectroscopy. It is found that the state of unoccupied molecular orbitals of the top molecular layer (TML) becomes occupied by the electrons transferred from the Ca atoms. The work function of the heavily doped TML of PC61BM film is smaller than that of metal Ca, and thus the contact between the TML and metal Ca is Ohmic. A transition layer (TL) of several molecular layers forms beneath the TML due to the diffusion of the Ca atoms. The TL is conductive and aligns its Fermi level with the negative integer charge transfer level of the interior PC61BM. The built-in electric field in the TL facilitates the electron transport from the interior of the PC61BM film to the TML.

Published in AIP Advances

ISSN: 2158-3226 (Online)
Publisher: AIP Publishing LLC
Country of publisher: United States
LCC subjects: Science: Physics
Website: http://aipadvances.aip.org/

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