The electroluminescence (EL) of Tb 3+ -doped anodic Ta 2 O 5 films in the presence of H 2 O 2 was studied. Since the EL of the dopant Tb 3+ ion shows the same potential (U) dependence as the background EL, light emission from Tb 3+ can be used to monitor electrochemical processes at the oxide/solution interface. In the rising part of the (EL,U) curve, both the hole injection rate and the radiative recombination efficiency increase. This gives rise to a quadratic dependence of the intensity on the current. The EL is not influenced by the rotation rate; ring-disk experiments show the hole injection current to be kinetically limited