Effect of oxygen annealing on spatial atomic layer deposited aluminum oxide/silicon interface and on passivated emitter and rear contact solar cell performance

Abstract

In this study, aluminum oxide (Al2O3) thin films are deposited via spatial atomic layer deposition on p-type silicon wafer. Then, a post-deposition annealing is performed in oxygen to activate the field-effect and chemical passivation. The annealing temperature is varied from 300 °C to 750 °C, and its effect on the structural properties and carrier lifetime of Al2O3/Si is investigated. The results show that at the annealing temperature of 600 °C, the highest minority carrier lifetime obtained is 446.5 μs and maximum surface recombination rate is 22.4 cm/s. Annealing temperatures higher than 600 °C lead to deteriorate surface passivation due to insufficient hydrogen passivation and structural change from AlO4 to AlO6 that cause low oxide fixed charge. Photovoltaic performance is simulated and compared with experimental results. The simulation shows that the p-type passivated emitter and rear contact (PERC) solar cell with the Al2O3 single layer annealed at 600 °C can have open-circuit voltage (Voc) of 678 mV and conversion efficiency (η) of 21.96%, while the PERC solar cell with SiNx:H/Al2O3 doubled layer can achieve Voc of 679.7 mV and η of 22.03%, which is very close to the upper limit in the case of ideal rear passivation. The simulation is in a good agreement with the fabricated PERC solar cell showing Voc = 679.2 mV and η = 21.6%.