CF4/O-2 dry etching of textured crystalline silicon surface in a-Si : H/c-Si heterojunction for photovoltaic applications

We investigated a dry cleaning procedure of the crystalline substrate, both mono- and multi crystalline silicon, to leave an uncontaminated surface us ing an etching process involving CF4/O-2 mixture. A detailed investigation was performed to find compatibility and optimisation of amorphous layer dep ositions both on flat and textured silicon by changing the plasma process p arameters. We found evidence that plasma etching acts by removing the nativ e oxide and the damages of textured silicon and by leaving an active layer on silicon surface suitable for the emitter deposition. SEM analysis confir med that it is possible to find plasma process conditions where no apprecia ble damages and change in surface morphology are induced. By using this pro cess we achieved on amorphous crystalline heterostructure a photovoltaic co nversion efficiency of 13% on 51 cm(2) and 14.5% on 1.26 cm(2) active area. We also investigated compatibility of the process with industrial producti on of large area devices. (C) 2001 Elsevier Science B.V. All rights reserve d.