Mid-infrared intraband electroluminescence on planar interdigitated electrodes

Five-micron electroluminescence is realized in a planar device using a film of core/shell HgSe/CdS colloidal quantum dots deposited on interdigitated electrodes. The efficiency is comparable to a prior device in a traditional vertical stack, and the fabrication is simplified. Since the emission is from the intraband transition of the HgSe cores, the device is driven by a single-charge carrier type, and this allows identical electrodes of arbitrary design, without additional charge transport layers. Basic studies of the effects of doping and temperature are done with an added bottom gate electrode. The planar structure eliminates the requirement of the infrared transparency of the electrodes. With a back reflector, a dielectric spacer, and optimized electrode spacing and periodicity, a device emitting at 5 μm achieved an external electron-to-photon conversion of 15% and a power conversion efficiency of 0.085%.