Boron emitters from doped PECVD layers for n-type crystalline silicon solar cells with LCO

Abstract

The intensified research into n-type silicon solar cells over the last few years let the application of boron doped emitters in suitable cell concepts become the preferred method to form the necessary p-n-junction. In this study an alternative process to fabricate a boron doped emitter via diffusion from a PECV-deposited doping source is presented and optimized for n-type crystalline silicon solar cell concepts. Doping profiles with a high surface concentration in combination with low emitter saturation current density values are achieved for improved contact and passivation characteristics. The boron emitter profile is compatible with various contacting techniques i.e. screen printing and vapour deposited Al, allowing for low-resistant contacting with Ag/Al pastes or sputtered Al. The comparably low emitter saturation current density j0E of 44 fA/cm² allows for a VOC of 666 mV, and thereby a cell efficiency of 19.7% is demonstrated on a large area (156.25 cm²) solar cell.