Effect of diffusion parameters on emitter formation in silicon solar cells by proximity rapid thermal diffusion

Abstract

N-type emitters have been formed in p-type monocrystalline silicon with good uniformity and high peak doping concentration by proximity rapid thermal diffusion (PRTD). High diffusion rates are achievable for relatively low temperatures (< 1000°C) with the addition of O2 to the N2 diffusion atmosphere. Solar cells have been prepared from the diffused samples to assess their performance and efficiencies of up to 6.0% have been achieved. The devices possess high series resistance and high recombination rates amongst other factors which limit their performance. Reducing the junction depth improves Jsc and efficiency but is accompanied by degrading shunt resistance and FF for junction thicknesses below ~ 400nm. Further refinements of cell processing should improve efficiency and result in a diffusion process for forming shallow emitters for application to microstructured devices such as micropillar radial junction solar cells.