Pathways for efficiency improvements of industrial PERC silicon solar cells

Abstract

The global manufacturing capacity of Passivated Emitter and Rear Cell (PERC) devices on p-type Czochralski-grown silicon (Cz-Si) wafers is increasing rapidly. This paper analyses various industrial process improvements carried out in our lab to improve the efficiency of large-area Cz-Si PERC solar cells from 20.7% to 21.9%. The key improvements presented in this paper include the transition from line to dot-shaped laser openings in the rear dielectric stack, a dual printing approach for the front fingers and implementation of a laser-doped selective-emitter structure. A nanosecond (ns) pulsed laser source with 532 nm wavelength was used for both the rear dielectric ablation and the front laser doping. By adopting a systematic power loss analysis approach and targeting the largest power loss mechanisms at various stages of development, the best efficiency of the solar cells in this experimental study was improved from 20.7% to 21.9%. Pathways for further improvements in efficiency are analysed, including the application of passivated-contact structures in a PERC-like cell.