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 similar to 1050 degrees C for 30 similar to 90 min for activation. Boron emitters were activated at 1000 degrees C or higher, while phosphorus emitters were activated at 950 degrees C. QSSPC measurements show that the implied V-oc of boron emitters increases about 15mV 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 mu s to 14 mu s. PC1D simulation based on these results shows that, for p-type implanted solar cells, increasing the annealing temperature and time abruptly decreases the efficiency (Delta eta(abs) = -1.3%), while, for n- type implanted solar cells, deep junction annealing increases the efficiency and V-oc, especially (Delta eta(abs) = +0.4%) for backside emitter solar cells.