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Two types of silicon (Si) substrates (40 n-type with uniform base doping and 40 n/n + epitaxial wafers) from the silicon industry rejects were chosen as the starting material for low-cost concentrator solar cells. They were divided into four groups, each consisting of 20 substrates: 10 are n/n + and 10 are n substrates, and the solar cells were prepared for different diffusion times (45, 60, 75 and 90 min). The fabricated solar cells on n/n + substrates (prepared with a diffusion time of 75 min) showed better parameters. In order to improve their performances, particularly the fill factor, 20 new solar cells on n/n + substrates were fabricated using the same procedure (the diffusion time was 75 min)—but with four new front contact patterns. Investigation of current–voltage ( I – V ) characteristics under AM 1.5 showed that the parameters of these 20 new solar cells have improved in comparison to previous solar cells' parameters, and were as follows: open-circuit voltage ( V OC =0.57 V); short circuit current ( I SC =910 mA), and efficiency ( η =9.1%). Their fill factor has increased about 33%. The I – V characteristics of these solar cells were also investigated under different concentration ratios ( X ), and they exhibited the following parameters (under X =100 suns): V OC =0.62 V and I SC =36 A. |
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