Thermal Laser Separation of PERC and SHJ Solar Cells
This article investigates thermal laser separation (TLS) on p-type Czochralski-grown silicon (Cz-Si) passivated emitter and rear cells (PERC) and n-type Cz-Si heterojunction (SHJ) solar cells. The TLS comprises of two laser-based processes: the crack initiation by a scribe laser and the crack propagation by a cleave process leading to separated cells with smooth edge surfaces. The sole impact of the cleave process on the cells' passivation layers is examined by performing it without the initial scribe, not separating the samples. By means of photoluminescence imaging, different cleave laser powers PC on passivated PERC and SHJ cell precursors are investigated, and the optimum PC values are then chosen for the processing of metallized and fired host cells with half cell and shingle cell layouts. Both, the cleave process as well as the complete TLS process are then separately performed in order to investigate the effect of each individual process by SunsVOC measurements taken before and after processing. For monofacial PERC cells, a drop in pseudofill factor DpFF = - 0.3%abs is recorded after TLS of the host cell into five shingle cells with 31.35 mm cell width. The effect on bifacial SHJ cells is stronger with DpFF = - 2.1%abs. Thereby, the cleave process itself does not induce significant losses in the cell performance for both cell types. The main losses are attributed to the recombination at the newly created unpassivated edges after complete TLS.