Wafer-Scale Growth of Silicon Microwire Arrays for Photovoltaics and Solar Fuel Generation

Abstract

Silicon microwire arrays have recently demonstrated \ntheir potential for low-cost, high-efficiency photovoltaics and photoelectrochemical \nfuel generation. A remaining challenge to making \nthis technology commercially viable is scaling up of microwirearray \ngrowth. We discuss here a technique for vapor–liquid–solid \ngrowth of microwire arrays on the scale of six-inch wafers using \na cold-wall radio-frequency heated chemical vapor deposition furnace, \nenabling fairly uniform growth over large areas with rapid \ncycle time and improved run-to-run reproducibility. We have also \ndeveloped a technique to embed these large-area wire arrays in \npolymer and to peel them intact from the growth substrate, which \ncould enable lightweight, flexible solar cells with efficiencies as high \nas multicrystalline Si solar cells. We characterize these large-area \nmicrowire arrays using scanning electronmicroscopy and confocal \nmicroscopy to assess their structure and fidelity, and we test their \nenergy-conversion properties using a methyl viologen (MV^(2+/+) ) \nliquid junction contact in a photoelectrochemical cell. Initial photoelectrochemical \nconversion efficiencies suggest that the material \nquality of these microwire arrays is similar to smaller (∼1 cm^2 ) \nwire arrays that we have grown in the past, indicating that this \ntechnique is a viable way to scale up microwire-array devices.