Large area n-type silicon solar cells with selective front surface field and screen printed aluminium-alloyed rear emitter

Abstract

Large area n-type silicon solar cells with a screen-printed aluminum rear side emitter are mainly limited by their front surface recombination velocity. In order to overcome this limitation, we use an industrially applicable etch-back process to create a selective front surface field (s-FSF). This process was developed for the formation of a single diffusion selective emitter on p-type silicon; it generates a deep doping profile with a low surface concentration which results in an excellent emitter saturation current and a highest independently confirmed stable cell efficiency of 18.7% on 5” p-type Cz silicon. In this work we focus on the applicability of this process to n-type silicon. 6” solar cells with different front side etchback depths have been processed from n-type silicon leading to a highest efficiency of 18.5% for a s-FSF cell and an average gain of 0.8%abs compared to cells with a homogeneous FSF. We furthermore investigate the quality of the etch-back FSF and the screen printed alloyed emitter from different pastes by QSSPC measurements.