Effect of an electric field on photoluminescence of cadmium selenide nanocrystals

Abstract

We have demonstrated a difference in the nature of the effect of a strong external electric field (>10 5 V/cm) on the photoluminescence of cadmium selenide nanoparticles of different shapes. We have determined a correlation between the magnitude of the external electric field and the average photoluminescence decay time for two types of nanoparticles: "quantum dots" and nanorods. We discuss the mechanism for the effect of an electric field on the photoluminescence of both types of nanoparticles.Keywords: "quantum dots", nanorods, cadmium selenide, kinetics of photoluminescence, polarization, electric field, Stark effect. Introduction.Optoelectronic devices designed on the basis of nanostructures that are controllable by an external electric field and that contain quantum-confined semiconductor nanoparticles allow for full integration of the optical component and conventional semiconductor microelectronics components. Effective control of the optical absorption and luminescence of such structures using an external electric field, as predicted by theory, can be fully realized in structures such as "quantum dots" [1, 2]. Chemically synthesized semiconductor nanocrystals, as representatives of this type of structure, also exhibit a dependence of the optical properties on the magnitude of the external field (the quantum-confined Stark effect for absorption [3], and also the Stark shift and quenching of luminescence on emission of light [4]). Luminophores based on such nanostructures in combination with blue light-emitting diodes are of special practical interest for designing economical sources of white light [5]. In contrast to "quantum dots" (called nanocrystals in the following),ànanorods have quantum confinement only in two spatial dimensions, which is why there is a difference in the manifestation of the effect of an external electric field and polarization selectivity of the optical properties relative to the field vector.Using an external electric field to control photoluminescence (PL) of semiconductor nanocrystals and nanorods requires detailed study of the spectral and kinetic characteristics of such structures as a function of the magnitude of the applied external electric field. The structures best studied to date are based on cadmium selenide compounds. However, the specific details of the mechanisms for radiative and nonradiative recombination in nanorods in the presence of a strong external electric field have not been fully identified. In particular, the difference in the mechanisms for quenching of photoluminescence for nanorods and nanocrystals, and also the effect of the orientation of nanorods relative to the external field on their photoluminescence kinetics, still remain insufficiently studied. Study of quenching of photoluminescence for single nanorods in an external electric field also has not provided a clear answer to the question concerning the possible mechanism of action for the field on radiative recombination of electron×donor pairs in nanoparticles [6][7][8][9][10].The aim of this work ...

Properties of Nematic Liquid Crystals Doped with CdSe/ZnS Semiconductor Nanoparticales

“…б -изменение относительной интенсивности ФЛ КТ CdSe/ZnS от напряженности электрического поля Тушение интенсивности ФЛ в нашем случае может быть связано с уменьшением вероятности прямой излучательной рекомбинации электрона и дырки [49][50][51] в результате уменьшения перек-рытия их волновых функций при приложении внешнего электрического поля. Более того, на межфазной границе органических молекул НЖК с малым электронным сродством и полупровод-никовых нанокристаллов с большим сродством может происходить эффективное разделение заряда [46,52].…”

Electric Field Effects on Photoluminescence of CdSe Nanoparticles in a PMMA Film

“…Gurinovich et al [43] also measured electric field effects on absorption and photoluminescence of CdSe nanoparticles with a diameter of 4 nm in PMMA and reported the tremendous decreases both in the absorption intensity at the exciton peak and in the photoluminescence intensity by the application of 0.2 MV· cm −1 . Such remarkable decreases both in PL intensity and in absorption intensity were not observed in the present E-A and E-PL measurements.…”

Quantum-Dot-Based Solid-State Lighting With Electric-Field-Tunable Chromaticity

“…The necessary wavelength shifts are thus relatively large, and it is not obvious whether they are practically achievable. The application of a static electric field to semiconductor heterostructures results in level shifting of the confined electrons and holes (Stark shifts) which in turn lead to shifts in the emission spectra when radiative recombination occurs [32]- [34]. These spectral shifts can be large for some geometries and/or dimensionalities.…”

“…As discussed in Section II, it is well known [32]- [34] that electric fields cause a spatial separation of the electron and hole, and hence a decrease in the cross-section for light absorption. These changes in absorption cross-section are most pronounced near the band edge, and if the band edge has been tuned to the green or red, absorption in the blue is likely to be into high-lying levels far from the band edge where changes in absorption crosssection are typically small [34]- [36].…”

“…These changes in absorption cross-section are most pronounced near the band edge, and if the band edge has been tuned to the green or red, absorption in the blue is likely to be into high-lying levels far from the band edge where changes in absorption crosssection are typically small [34]- [36].…”