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Investigation of the buried planar interfaces in multi-layered inverted organic solar cells using x-ray reflectivity and impedance spectroscopy
Srivastava S.B., Modi M.H., ,
Published in Institute of Physics Publishing
PMID: 30641510
Volume: 31
Issue: 12
The hole and electron extracting interlayers in the organic solar cells (OSCs) play an important role in high performing devices. The present work focuses on an investigation of Zinc oxide/bulk heterojunction (ZnO/BHJ) and BHJ/MoO x (Molybdenum oxide) buried planar interfaces in inverted OSC devices using the optical contrast in various layers along with the electrical measurements. The x-ray reflectivity (XRR) analysis demonstrates the formation of additional intermixing layers at the interfaces of ZnO/BHJ and BHJ/MoO x . Our results indicate infusion of PC71BM into ZnO layer up to ∼4 nm which smoothen the ZnO/BHJ interface. In contrast, thermally evaporated MoO x molecules diffuse into PTB7-Th dominant upper layers of BHJ active layer resulting in an intermixed layer at the interface of MoO x /BHJ. The high recombination resistance (∼5 kω cm 2 ) and electron lifetime (∼70 μs), obtained from the impedance spectroscopy (IS), support such vertical segregation of PTB7-Th and PC71BM in the active layer. The OSC devices, processed in ambient condition, exhibit high power conversion efficiency of 6.4\%. We consider our results have great significance to understand the structure of buried planar interfaces at interlayers and their correlation with the electrical parameters representing various interfacial mechanisms of OSCs. © 2019 IOP Publishing Ltd.
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Published in Institute of Physics Publishing
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