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Ethanedithiol Treatment of Solution‐Processed ZnO Thin Films: Controlling the Intragap States of Electron Transporting Interlayers for Efficient and Stable Inverted Organic Photovoltaics
Author(s) -
Bai Sai,
Jin Yizheng,
Liang Xiaoyong,
Ye Zhizhen,
Wu Zhongwei,
Sun Baoquan,
Ma Zaifei,
Tang Zheng,
Wang Jianpu,
Würfel Uli,
Gao Feng,
Zhang Fengling
Publication year - 2015
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201401606
Subject(s) - passivation , materials science , nanocrystal , photovoltaics , optoelectronics , organic solar cell , energy conversion efficiency , hybrid solar cell , recombination , zinc , chemical engineering , thin film , nanotechnology , polymer solar cell , polymer , photovoltaic system , layer (electronics) , composite material , chemistry , metallurgy , ecology , biochemistry , gene , engineering , biology
The surface defects of solution‐processed ZnO films lead to various intragap states. When the solution‐processed ZnO films are used as electron transport interlayers (ETLs) in inverted organic solar cells, the intragap states act as interfacial recombination centers for photogenerated charges and thereby degrade the device performance. Here, a simple passivation method based on ethanedithiol (EDT) treatment is demonstrated, which effectively removes the surface defects of the ZnO nanocrystal films by forming zinc ethanedithiolates. The passivation by EDT treatment modulates the intragap states of the ZnO films and introduces a new intragap band. When the EDT‐treated ZnO nanocrystal films are used as ETLs in inverted organic solar cells, both the power conversion efficiency and stability of the devices are improved. The control studies show that the solar cells with EDT‐treated ZnO films exhibit reduced charge recombination rates and enhanced charge extraction properties. These features are consistent with the fact that the modulation of the intragap states results in reduction of interfacial recombination as well as the improved charge selectivity and electron transport properties of the ETLs. It is further demonstrated that the EDT treatment‐based passivation method can be extended to ZnO films deposited from sol–gel precursors.