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Title: Pulsed laser deposition of zinc oxide thin films for optoelectronic applications
Author: Franklin, Joseph B.
ISNI:       0000 0004 2728 8358
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2012
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Zinc oxide (ZnO) thin films have great promise for a wide range of optoelectronic applications, however controlling crystallinity and stoichiometry at low processing temperatures remains a challenge. Pulsed laser deposition (PLD) is a versatile technique that allows precise control the film properties. The crystallinity and electrical properties can, theoretically, be tuned by altering a wide variety of deposition parameters. However, until now there has been little work performed exploring PLD as a technique for the preparation of thin films at low temperature, for use in optoelectronic applications. In this thesis, PLD is demonstrated as a highly appropriate technique for the preparation of semiconducting and electrically conducting transparent films, over a wide range of substrate temperatures applicable for optoelectronic grade substrates. Deposition conditions are identified allowing the low temperature deposition of ZnO directly onto functional organic poly(3-hexylthiophene) (P3HT) coated substrates. To demonstrate the applicability of this methodology the preparation of conventional architecture hybrid (inorganic:organic) photovoltaic devices is outlined with no degradation to the microstructure, optical or electrical properties of the P3HT observed. The methodology is widely applicable for depositing oxide interlayers multilayer organic devices. In this thesis, the role of ZnO is investigated as i) an exciton dissociation and electron transporting layer in hybrid devices, ii) an optical spacing layer in organic bulk heterojunction photovoltaic devices and iii) as a transparent conducting oxide (when doped with A1) as a top contact for organic optoelectronic devices. Device performance is optimised through careful control of PLD parameters. In each device and in free-standing thin films the microstructure, morphology and crystallographic nature of the as-deposited ZnO is studied by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The electrical properties are studied in both operational devices and by 4-point probe measurements.
Supervisor: McLachlan, Martyn ; Ryan, Mary Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral