SiC-based and Al203-based Si solar cells, together with a single p-n (Si) homo-junction solar cell, have been investigated. Open-circuit voltage, short circuit current and cell efficiency for each solar cell have been measured, under different solar concentrations. The parameters for all cells were improved with higher concentration levels. The open circuit voltage reached a maximum value under 500 sun concentration for each cell. Efficiency values of 31.4%, 27.5% and 20%for the SiC-based cell, Al203-based cell and the homo-junction cell, respectively, have been obtained, when appropriate cooling systems were used. Such difference is presumably due to the more efficient cooling mechanism of the substrates, being more efficient for SiC. This characteristic, together with cost considerations and mechanical properties, makes the SiC substrate a good candidate to support Si thin film solar cells.