Near-Unity Quantum Yield in Semiconducting Nanostructures: Structural Understanding Leading to Energy Efficient Applications

Core/shell nanocrystal quantum dots (NQDs) have shown great potential as efficient electroluminescent materials in devices like down-conversion phosphors and light-emitting diodes (LEDs). The efficiency of these devices is nonlinearly enhanced by the use of high quantum yield (QY) materials. Though relatively high QY materials with inherent advantages for use in device applications are achieved by thick-shell CdSe/CdS NQDs, their QY is not anywhere near unity due to lack of correlation of the microstructure with their photophysical properties. Here, in this Letter, we show that the control of interfacial defects is crucial to achieve a near-unity QY using microstructure studies of CdSe/CdS NQDs. Simple unoptimized LEDs obtained from these NQDs as the active layer demonstrate performances in excess of 7000 Cd/m(2) with a power conversion efficiency of similar to 1.5 Im/W that is comparable to those of the best NQD-based LEDs (1-3%) despite the absence of an electron-injecting buffer layer.