Metal oxide/organic interface investigations for photovoltaic devices

This thesis outlines investigations of metal oxide / organic interfaces in photo- voltaic devices. It focuses on device instabilities originating from the metal oxide layer surface sensitivity and it presents suggested mechanisms behind these in- stabilities. A simple sol-gel solution deposition technique for the fabrication of stable and highly performing transparent conducting mixed metal oxides (ZnMO) is presented. It is demonstrated that the use of amorphous, mixed metal oxides allows improving the performance and stability of interfacial charge extraction layers for organic solar cells. Two novel ternary metal oxides, zinc-strontrium- oxide (ZnSrO) and zinc-barium-oxide (ZnBaO), were fabricated and their use as electron extraction layers in inverted organic photovoltaics is investigated. We show that using these ternary oxides can lead to superior devices by: prevent- ing a dipole forming between the oxide and the active organic layer in a model ZnMO / P3HT:PCBM OPV as well as lead to improved surface coverage by a self assembled monolayer and promote a significantly improved charge separation efficiency in a ZnMO / P3HT hybrid device. Additionally a spectroscopic technique allowing a versatility of characterisa- tion for long-term stability investigations of organic solar cells is reported. A device instability under broadband light exposure in vacuum conditions for an inverted ZnSrO/PTB7:PC71BM OPV is observed. Direct spectroscopic evidence and electrical characterisation indicate the formation of the PC71BM radical an- ion associated with a loss in device performance. A charge transfer mechanism between a heavily doped oxide layer and the organic layers is suggested and dis- cussed.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2014

Author dc:creator

• Pachoumi, Olympia

• photovoltaics
• solar cell
• organic solar cell
• organic photovoltaics
• metal oxide
• electron extraction layer
• organic semiconductors
• organic electronics
• mixed metal oxides
• hybrid solar cells
• sol-gel
• charge accumulation spectroscopy

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/da502761-fa28-408a-9b89-85e0e4ff4795/download

Language dc:language

en

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.16614

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/246263