Stability of Al2O3 and Al2O3/a-SiNx:H stacks for surface passivation of crystalline silicon

The thermal and ultraviolet (UV) stability of crystalline silicon (c-Si) surface passivation provided by atomic layer deposited Al2O3 was compared with results for thermal SiO2. For Al2O3 and Al2O3/a-SiNx:H stacks on 2 Ω cm n-type c-Si, ultralow surface recombination velocities of Seff<3 cm/s were obtained and the passivation proved sufficiently stable (Seff<14 cm/s) against a high temperature “firing” process (>800 °C) used for screen printed c-Si solar cells. Effusion measurements revealed the loss of hydrogen and oxygen during firing through the detection of H2 and H2O. Al2O3 also demonstrated UV stability with the surface passivation improving during UV irradiation.