Electrodeposited Light-Emitting Nanojunctions
By Xing, Wendong; Yan, Wenbo; Ayvazian, Talin; Wang, Yong; Potma, Eric O. & Penner, Reginald M.
Published in Chemistry of Materials
2013
Abstract
Electroluminescent (EL) metal-semiconductor-metal nanojunctions are prepared by electrodepositing nanocrystalline cadmium selenide (nc-CdSe) within ∼250 nm gold (Au) nanogaps prepared by focused ion beam milling. The electrodeposition of nc-CdSe is carried out at two temperatures: 20 °C (“cold�) and 75 °C (“hot�), producing mean grain diameters of 6 ± 1 nm and 11 ± 2 nm, respectively, for the nc-CdSe. Light-emitting nanojunctions (LEnJs) prepared at both temperatures show a low threshold voltage for light emission of <2 V; just above the 1.74 eV bandgap of CdSe. The EL intensity increases with the injection current and hot-deposited LEnJs produced a maximum EL intensity that is an order of magnitude higher than the cold-deposited LEnJs. Emitted photons are bimodal in energy with emission near the band gap of CdSe, and also at energies 200 meV below it; consistent with a mechanism of light emission involving the radiative recombination of injected holes with electrons at both band-edge and defect states. The quantum yield for “hot� electrodeposited nc-CdSe LEnJs is comparable to devices constructed from single crystalline nanowires of CdSe, and the threshold voltage of 1.9 (±0.1) V (cold) and 1.5 (±0.2) V (hot) is at the low end of the range reported for CdSe nanowire based devices.