Phosphorous diffusion through silicon nitride thin film for selective emitter application

In this paper, we present a concept of selective emitter silicon solar cells fabrication. The most common ways for selective emitter formation are using the laser processing after the phosphorous thermal diffusion step. In this work, we propose to start with PECVD deposition of a thin silicon nitride (SiNx) layer before performing the phosphorous diffusion process. The purpose is first to open the fingers area by laser ablation and then perform one diffusion step both through the SiNx barrier layer and directly on the ablated pattern. This ablated pattern is dedicated to the subsequent front metallic contacts. This way, selective emitter structures with various sheet resistance couples (Low, High) could be obtained. The high sheet resistance corresponds to the SiNx covered area and the low one is displayed on the ablated area. The phosphorous diffusion process through the SiNx barrier layer was controlled by emitter sheet resistance and QSSP life-time measurements. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim