Enhancing Performance of a PERC Type Solar Cell Utilizing Improved Laser Ablation Techniques

Abstract

This study has attempted to build understanding of the effect of laser parameters including laser energy, pulse duration, and beam size on dielectric ablation characteristics for Passivated Emitter Rear Cell (PERC) type solar cells. The investigated composite dielectric layer consists of the bottom Al−oxide layer (~20 nm) and the top Si−nitride layer (~70 nm) with an interlayer of Si−oxynitride (~25 nm). Dielectric layers were deposited using PECVD on a monocrystalline (100) Si wafer and contacts were made by screen printing utilizing Ag paste on the front side and Al paste on the rear side. Different contact geometries were created to understand the effect of contact geometry on ablation−induced metallurgical damage and thus on the performance of cells. The study indicated that the usage of Ultraviolet picosecond laser with a dash contact pattern resulted in the highest cell efficiency over 22%. Other laser energies (Infrared, Green) with pulse duration (nanoseconds, picoseconds, and femtoseconds) either led to more damage or incomplete contact opening. The extent and area of ablation−induced damage to the substrate showed dependence on the contact pattern/geometry chosen, the spot−size and spot overlapping criteria followed. This study has presented a detailed discussion for recommending an optimized rear contact pattern geometry and laser ablation parameters considering metallurgical damages, the charge collection area and minority carrier lifetime of the fabricated PERC type solar cell