Charge Carrier Transport Mechanism in Ta2O5, TaON and Ta3N5 Studied by Polaron Hopping and Bandlike Models

Abstract

TaON and Ta3N5 are considered promising materials for photocatalytic and photoelectrochemical water splitting. But their counterpart Ta2O5 does not have good photocatalytic performance. This may cause by the different charge carrier transport mechanism in Ta2O5, TaON and Ta3N5 which are not well understood yet. Here, we investigated the charge transport mechanism in Ta2O5, TaON, and Ta3N5 by polaron and bandlike models. We find the charge transfer mechanism is small polaron hopping in Ta2O5. In TaON and Ta3N5, small polaron may not occur, and the charge may transfer through bandlike mechanism. The calculated mobility using effective mass approximation are not consistent with experimental observation. This study sets a foundation understanding of charge transport in oxynitrides and nitrides. A more accuracy model or understanding is needed to rationalize the calculated results and experimental observations in the future.