Locally-confined electrodeposition of Cu(In,Ga)Se 2 micro islands for micro-concentrator solar cells

The thin-film micro-concentrator solar cell concept promises to significantly reduce the consumption of the critical raw materials In and Ga by using a micro lens array to illuminate a regular array of Cu(In,Ga)Se 2 micro solar cells. We present the materials-efficient fabrication of micro solar cells by electrodeposition into holes inside a SiO 2 insulating matrix. The electrodeposition process shows a strong dependence on the hole size due to lateral diffusion in the solution, leading to faster deposition at the circumference of the holes. A calibration curve for the deposited CuInSe 2 thickness as a function of hole size is deduced. Cu(In,Ga)Se 2 micro solar cells were fabricated by sequential deposition of Cu and In-Ga, followed by a selenization process, leading to devices with 4.6% efficiency under 34 suns. Using finiteelement simulations, the heat transport in the microconcentrator solar cells is shown to be beneficial.