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Title: The role of defects in the radiation damage of solar cells
Author: Peters, Janice Wendy
ISNI:       0000 0001 3485 2138
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 1993
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Deep levels within the bandgap of solar cells are particularly important because they reduce the minority carrier diffusion length and hence limit the possible mission length of satellites. These deep levels are introduced by ambient high energy radiation fluxes present in Space. Identification and characterisation of these levels is therefore important if solar cell performance and useful power output are to be extended or improved. Previous studies of radiation effects on silicon solar cells are reviewed in detail, including defect control and basic aspects of defect characterisation. The review also incorporates an appraisal of the role of DLTS in defect studies. Two series of silicon solar cells have been investigated in the present work: a range of float zone cells with boron content covering almost three orders of magnitude and a series of Czochralski cells of varying oxygen content which includes two batches of specially designed and fabricated cells with a denuded - gettering system. Changes in short circuit current and spectral response as a function of radiation fluence, boron doping concentration and oxygen content of the cell have been investigated and compared to changes that were observed in the structure of the Deep Level Transient Spectrometry (DLTS) spectra for these cells. The Photon Effect, observed in irradiated float zone silicon solar cells, has been reconsidered as a result of recent developments in defect studies and improvements in the sensitivity of deep level measurements. The deep level previously assigned as being responsible for the Photon Effect, the boron-oxygen-vacancy (B-O-V), has been reassigned as the Bᵢ Cs defect. However more importantly a second defect has been observed to play a key interactive role in the Photon Effect. This level is a midgap level with a relatively large capture cross section at Ev+ 0.52eV.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Satellite