Tunable excited state energy transfer in image[image

A series of heterobimetallic crystals doped with various concentrations of image ions have been studied using steady-state and time-resolved spectroscopy. We report the details of energy transfer between the image donors and image ions in these single crystals. While characteristic luminescence from the image ions is found to be the result of both radiative and non-radiative electronic energy transfer from the mixed-metal donors, the dominant energy transfer mechanism is found to change with increasing dopant concentration. Radiative energy transfer is found to dominate at very low concentrations, while exchange is the proposed mechanism at high concentrations. For moderate doping (10% image), an excitonic diffusion model is proposed and we are able to calculate the rate of energy transfer.