Effect of High-Temperature Annealing on Ion-Implanted Silicon Solar Cells

Abstract

P-type and n-type wafers were implanted with phosphorus and boron, respectively, for emitter formation and were annealed subsequently at 950∼1050∘Cfor 30∼90 min for activation. Boron emitters were activated at1000∘Cor higher, while phosphorus emitters were activated at950∘C. QSSPC measurements show that the impliedVocof boron emitters increases about 15 mV and theJ01decreases by deep junction annealing even after the activation due to the reduced recombination in the emitter. However, for phosphorus emitters the impliedVocdecreases from 622 mV to 560 mV and theJ01increases with deep junction annealing. This is due to the abrupt decrease in the bulk lifetime of the p-type wafer itself from 178 μs to 14 μs. PC1D simulation based on these results shows that, for p-type implanted solar cells, increasing the annealing temperature and time abruptly decreases the efficiency (Δηabs=−1.3%), while, for n-type implanted solar cells, deep junction annealing increases the efficiency andVoc, especially (Δηabs=+0.4%) for backside emitter solar cells.