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Title: Electrodes for top-illuminated organic photovoltaic devices
Author: Tyler, Martin S.
ISNI:       0000 0004 6350 8848
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2016
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The work in this thesis focuses on the development of electrodes for top-illuminated organic photovoltaics (OPVs) and studies how their complex interactions with other layers affect the device. The development of a novel substrate electrode based on an Al | Cu bilayer capped with an ultra-thin Al layer is initially shown. This electrode offers the rare combination of high reflectivity, a very low work function of ~3.2 eV, and high stability towards oxidation. Photoelectron spectroscopy studies shows that an Al capping layer of ~1 nm in thickness is sufficient to block oxidation of the underlying Cu, which is remarkable given that the self-limiting oxide thickness for bulk Al is ≥2 nm. This promising substrate electrode is used to elucidate a new design rule for top-illuminated bulk-heterojunction OPVs. It is shown that for OPVs utilising high performance donor-type organic semiconductors in conjunction with a low work function electron extracting electrode, a barrier to hole-extraction spontaneously forms at the donor | electron-extracting electrode interface, blocking unwanted hole-extraction and negating the need for a hole-blocking layer, which simplifies the device architecture. This electrode design rule is underpinned by studies of the interfacial energetics with five widely used solution processed organic semiconductors as well as device based investigations. A novel organo-molybdenum oxide bronze is also developed which combines the function of wide band-gap interlayer for efficient hole-extraction with the role of a metal electrode seed layer, enabling the fabrication of highly transparent, low-sheet-resistance silver window electrodes for top-illuminated OPVs. Additionally, preliminary results relating to the fabrication of a model nanostructured reflective electrode are shown. This is designed to investigate the extent to which absorption of light can be enhanced in a top-illuminated OPVs by texturing the reflective substrate electrode.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry