Laser Induced Ablation and Doping Processes on High Efficiency Silicon Solar Cells

Abstract

Selective ablation and doping are processes common in crystalline silicon solar cell manufacturing intended to reduce the contact resistance between the metal and silicon and to enhance the blue response of the cells by means of a lightly doped emitter combined to a heavy doped contact area. These processes can particularly take advantage of the usage of laser technology since it enables the possibility to substitute high temperature furnace driven processes by low thermal budget, locally selective and highly flexible processes offered by lasers. One of the key points in transferring laser processes into production is the selection of the most adequate laser source and processing conditions. In this work we focus on the development of a laser assisted process of simultaneous ablation and doping for high efficiency crystalline silicon solar cells. Detailed process characterisation has been carried out as a function of different laser parameters. Evaluation of the sheet resistance of the doped area and dimensional and microstructural characterisation of laser transformed areas have been carried out for different process configurations. The impact of laser induced damage on the cell performance has been evaluated and strategies to minimise it are suggested.