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 cm n-type c-Si, ultralow surface recombination velocities of S-eff < 3 cm/s were obtained and the passivation proved sufficiently stable (S-eff < 14 cm/s) against a high temperature firing process (>800 degrees C) used for screen printed c-Si solar cells. Effusion measurements revealed the loss of hydrogen and oxygen during firing through the detection of H-2 and H2O. Al2O3 also demonstrated UV stability with the surface passivation improving during UV irradiation.