Francesca Buono

The Use of Solar Grade Silicon for Photovoltaic Devices 

Francesca Buono from Cosenza recently completed her Master of Philosoophy thesis at WIT on the topic of ‘The Use of Solar Grade Silicon for Photovoltaic Devices’. The external examiner was Prof Derek Ingham from the Department of Applied Mathematics at the University of Leeds. Prof Ingham’s research interests are many and varied and include computational fluid dynamics and the boundary element method amongst others.

Francesca’s thesis is concerned with the development of a model to predict the silicon powder elutriation in a fluidised-bed reactor for the silane decomposition reaction which represents the last step to ultrapure silicon. The growing PV market is primarily based on the crystalline silicon technology and already, the expected market expansion could be limited by the availability of a proper silicon feedstock. This so-called “solar grade” silicon (SoG-Si) serves as the base material for the crystalline silicon sheets used for the production of solar cells. In the first part of the thesis, photovoltaic systems are explained and why they need a solar grade silicon. In addition, a review of Solar Grade Silicon Technologies is given. The attention is then focused on the conversion of SiH4 to silicon. All the models presented in the literature are analysed and a new model is proposed to simulate the silane decomposition in a fluidized-bed reactor. The effects of silane inlet concentration are examined together with the gas velocity, temperature and the silicon fine powder elutriation. Francesca then compares the simulation results with experimental data available in the literature and with results obtained using classical fluidised-bed model proposed by other authors. Although the proposed model works well the last chapter proposes ways of validating the model.

The thesis was well received by the examiner who recommended awarding the Master of Philosophy degree to the candidate.