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

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 (V_oc) of 678 mV and conversion efficiency (η) of 21.96%, while the PERC solar cell with SiN_x:H/Al₂O₃ doubled layer can achieve V_oc 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 V_oc = 679.2 mV and η = 21.6%.