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 • C for 30∼90 min for activation. Boron emitters were activated at 1000 • C or higher, while phosphorus emitters were activated at 950 • C. QSSPC measurements show that the implied V oc of boron emitters increases about 15 mV and the J 01 decreases by deep junction annealing even after the activation due to the reduced recombination in the emitter. However, for phosphorus emitters the implied V oc decreases from 622 mV to 560 mV and the J 01 increases 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 (Δη abs = −1.3%), while, for n-type implanted solar cells, deep junction annealing increases the efficiency and V oc , especially (Δη abs = +0.4%) for backside emitter solar cells