Concentrator silicon solar cells from silicon industry rejects

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.