Hydrogen passivation of poly-Si/SiO\u3csub\u3ex\u3c/sub\u3e contacts for Si solar cells using Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e studied with deuterium

\u3cp\u3eThe interplay between hydrogenation and passivation of poly-Si/SiO\u3csub\u3ex\u3c/sub\u3e contacts to n-type Si wafers is studied using atomic layer deposited Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e and anneals in forming gas and nitrogen. The poly-Si/SiO\u3csub\u3ex\u3c/sub\u3e stacks are prepared by thermal oxidation followed by thermal crystallization of a-Si:H films deposited by plasma-enhanced chemical vapor deposition. Implied open-circuit voltages as high as 710 mV are achieved for p-type poly-Si/SiO\u3csub\u3ex\u3c/sub\u3e contacts to n-type Si after hydrogenation. Correlating minority carrier lifetime data and secondary ion mass spectrometry profiles reveals that the main benefit of Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e is derived from its role as a hydrogen source for chemically passivating defects at SiO\u3csub\u3ex\u3c/sub\u3e; Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e layers are found to hydrogenate poly-Si/SiO\u3csub\u3ex\u3c/sub\u3e much better than a forming gas anneal. By labelling Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e and the subsequent anneal with different hydrogen isotopes, it is found that Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e exchanges most of its hydrogen with the ambient upon annealing at 400 °C for 1 h even though there is no significant net change in its total hydrogen content.\u3c/p\u3