Si Microwire Solar Cells: Improved Efficiency with a Conformal SiO2 Layer

Abstract

Silicon microwire arrays have attracted considerable attention recently due to the opportunity they present as highly efficient and cost-effective solar cells. In this study, we report on efficient Si microwire array solar cells with areas of 1 cm2 and Air Mass 1.5 Global conversion efficiencies of up to 10.6%. These solar cells show an open-circuit voltage of 0.56 V, a short-circuit current density of 25.2 mA/cm2, and a fill factor of 75.2%, with a silicon absorption region that is only 25 μm thick. In particular, the maximum overall efficiency of the champion device is improved from 8.71% to 10.6% by conformally coating the wires with a 200 nm thick SiO2 layer. Optical measurements reveal that the layer reduces reflection significantly over the entire visible range.