Two-dimensional LBIC and Internal-Quantum-Efficiency investigations of grooved grain boundaries in multicrystalline silicon solar cells

摘要

Grain boundaries (GBs) in multicrystalline silicon (mc-Si) degrade the solar cells performances. To enhance the conversion efficiency of photovoltaic cells, preferential grooving was achieved in GBs in order to reduce their area and then their highly recombination effect. For this purpose, a chemical etching method in HF/HNO_3 solution was used. In this study, we show how grooved GB enables deep penetration of phosphorus and metallic contacts, which lead to a P-Al-co-gettering of undesired impurities. As a result, we observe a decrease in the recombination activity in regions close to the GBs as compared to ungrooved sample; this was investigated by the two-dimensional Light-Beam-Induced-Current (LBIC) imaging. In addition, we carried out a two dimensional representation of the Internal-Quantum-Efficiency (IQE), where images show an improvement of the electrical activity in grooved GBs.