AbstractsEngineering

Development of a high performance ultra-thin silicon solar cell on steel substrate

by Lu Wang




Institution: University of New South Wales
Department: Photovoltaics & Renewable Energy Engineering
Year: 2014
Keywords: steel substrate; Ultra-thin silicon; solar cells; high performance
Record ID: 1037860
Full text PDF: http://handle.unsw.edu.au/1959.4/54037


Abstract

This thesis addresses the design and development of a ~20 um mono-crystalline silicon solar cell on a robust and conductive substrate. The thin silicon of this solar cell is grown on a porous silicon layer and is then exfoliated and transferred onto a foreign substrate. The kerfless ultra-thin silicon approach not only significantly decreases the demand of silicon used in solar cell fabrication, but also enables the potential to achieve higher performance compared to conventional wafer approaches. In addition, the robust substrate turns the fragile thin silicon into a robust device, and allows the independent process of each surface. A high performance ultra-thin silicon solar cell has been designed, and the high performance design includes high Voc, high Jsc and high FF. PC1D modelling predicts a maximum efficiency of 25.4% with a Voc of 767 mV. First principle calculation gives a Voc of 757 mV, a Jsc of 39.5 mA/cm2 and a FF of 80.95% for this 20 um solar cell with a textured surface. Test structures made from epitaxial on FZ wafers enable the separation of surface properties from material quality, and allow the measurements of parameters that are difficult to be measured directly on ultra-thin silicon solar cells on steel. These test structures are utilized to analyze Voc losses at each fabrication step. A high performance fabrication process has been developed for the ultra-thin silicon solar cells on steel. The best planar solar cell with a thickness 20 um and area 1.21 cm2 had an efficiency of 12.1% with a Voc of 612.2 mV, a Jsc of 26.86 mA/cm2 and a FF of 73.7%. Shallow texturing is developed which contributes to significantly increase in Jsc, and material quality is improved resulting in improvement in Voc. The best textured solar cell with a thickness 18 um and area 4.00 cm2 had an efficiency of 16.8% with a Voc of 632.2 mV, a Jsc of 34.49 mA/cm2 and a FF of 77.2%. This efficiency is the highest for epitaxial layer on porous with layer transfer cells thinner than 40 um.