(TCSPC) measurements for QDs to QWQDs show three exponential radiative decay. Room temperature time correlated single photon counting PL spectra have been recorded at different temperatures (10K-300K). (PL) spectra from QDs to QWQDs shows high tunability which is not possible with single constituent semiconductor QDs. Strong red shift from ∼597 to ∼746 nm in photoluminescence Size of different QDs ∼5 to 7 nm were measured by transmission electron microscopy For shell coating we used modified version of successive ionic layer adsorption and reaction (SILAR). Quantum dots (HQDs) and CdSe/CdTe/CdSe quantum well-quantum dots (QWQDs) heterostructures.ĬdSe core QDs were synthesized using a kinetic growth method where QD size depends on reaction time. (CT) in type-II quantum confined heterostructure by comparing CdSe The results presented in this work demonstrate great opportunities for creating functional materials with programmable properties for electronics and optoelectronics. Furthermore, we attempted to extend the toolbox of the c-ALD to combine materials with intrinsically different properties, such as Au/CdS core/shell structures with substantial lattice mismatch. All core-shell multicomponent nanoparticles preserve narrow size distributions, phase crystallinity and shape homogeneity of the initial NCs. Using this technique, uniform layers of CdS and ZnS semiconductor shells were epitaxially grown on CdSe semiconductor cores with different shell combinations, leading to the precise control of the optical properties of these heterostructures. The c-ALD technique is based on self-limiting half-reactions of ionic precursors on the surface of a nanocrystal (NC) occurring at room temperature. We present a general strategy for a facile synthesis of complex multifunctional nanoscale materials via colloidal atomic layer deposition (c-ALD). These successes explain the continuing appeal of this field to a broad community of scientists and engineers, which in turn ensures even more exciting results to come from future exploration of this fascinating class of materials. We examine the considerable recent progress on these multiple fronts of nanocrystal research, which has resulted in the first commercialized QD technologies. Examples of such advanced control of nanocrystal functionalities include the following: interface engineering for suppressing Auger recombination in the context of QD LEDs and lasers Stokes-shift engineering for applications in large-area luminescent solar concentrators and control of intraband relaxation for enhanced carrier multiplication in advanced QD photovoltaics. A specific underlying theme is innovative concepts for tuning the properties of QDs beyond what is possible via traditional size manipulation, particularly through heterostructuring. The focus of this review is on recent advances in nanocrystal research related to applications of QD materials in lasing, light-emitting diodes (LEDs), and solar energy conversion. The field of nanocrystal quantum dots (QDs) is already more than 30 years old, and yet continuing interest in these structures is driven by both the fascinating physics emerging from strong quantum confinement of electronic excitations, as well as a large number of prospective applications that could benefit from the tunable properties and amenability toward solution-based processing of these materials. The ASE in the blue range has never been previously achieved using traditional NCs with type I carrier localization. We use these novel hetero-NCs to demonstrate efficient amplified spontaneous emission (ASE) that is tunable across a “difficult” range of green and blue colors. This effect leads to reduced optical-gain thresholds and can potentially allow lasing in the single-exciton regime, for which Auger recombination is inactive. We show that such hetero-NCs can exhibit strong repulsive exciton−exciton interactions that lead to significantly reduced excited-state absorption associated with NCs containing single electron−hole pairs. Here we explore a novel approach to achieve NC lasing in the Auger-recombination-free regime by using type II NC heterostructures that promote spatial separation of electrons and holes. The technological potential of NCs as lasing materials is, however, significantly diminished by highly efficient nonradiative Auger recombination of multiexcitons leading to ultrafast decay of optical gain. Size-controlled spectral tunability and chemical flexibility make semiconductor nanocrystals (NCs) attractive as nanoscale building blocks for color-selectable optical-gain media.
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