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A blue organic light-emitting diode (OLED) with silica-coated silver nanocubes (Ag@SiO2 NCs) inserted at the hole transporting layer/emission layer interface is reported. The localized surface plasmon resonance (LSPR) properties of the Ag@SiO2 NCs were characterized by the measured absorption spectra, stable-stated and transient photoluminescence, and calculated dipole radiation power. The results suggest that the Ag NCs significantly improved the radiation intensity of the nearby excitons due to their sharp corners and edges, but had less impact on the radiation rate of the excitons. The exciton recombination zone in the blue OLED was confirmed by a group of devices with an ultra-thin yellow emission layer located at different places, which helped to figure out the distribution of the excitons around the Ag@SiO2 NCs and deeply understand the coupling between the excitons and the Ag@SiO2 NCs. In our blue OLED, an appropriate distance between the Ag NCs and the excitons was realized by the SiO2 coating layer and the exciton distribution, which greatly improved the energy transfer between the excitons and the Ag NCs. In addition, the LSPR enhanced electric field around the Ag@SiO2 NCs improved the carrier injection at the hole transporting layer/emission layer interface and increased the current density of the blue OLED. Finally, the blue OLED with a simple triple layer structure achieved a high current efficiency of 51.1 cd A−1. [ABSTRACT FROM AUTHOR]

Transparent conducting oxides keep attracting strong scientific interest not only due to their promising potential for ‘transparent electronics’ applications but also due to their intriguing optical absorption characteristics. Materials such as In2O3 and Ga2O3 have complicated unit cells and, consequently, are interesting systems for studying the physics of excitons and anisotropy of optical absorption. Since currently no experimental data is available, for instance, for their dielectric functions across a large photon-energy range, we employ modern first-principles computational approaches based on many-body perturbation theory to provide theoretical-spectroscopy results. Using the Bethe–Salpeter framework, we compute dielectric functions and we compare to spectra computed without excitonic effects. We find that the electron–hole interaction strongly modifies the spectra and we discuss the anisotropy of optical absorption that we find for Ga2O3 in relation to existing theoretical and experimental data. [ABSTRACT FROM AUTHOR]

Excitons in high-purity crystals of Cu2O undergo a density-dependent lifetime that opposes Bose–Einstein condensation (BEC). This rapid decay rate of excitons at a density n has generally been attributed to Auger recombination having the form , where A is an exciton-Auger constant. Various measurements of A, however, have reported values that are orders-of-magnitude larger than the existing theory. In response to this conundrum, recent work has suggested that excitons bind into excitonic molecules, or biexcitons, which are short-lived and expected to be optically inactive. Of particular interest is the case of excitons confined to a parabolic strain well—a method that has recently achieved exciton densities approaching BEC. In this paper we report time- and space-resolved luminescence data that supports the existence of short-lived biexcitons in a strain well, implying an exciton loss rate of the form with a biexciton capture coefficient C(T) proportional to , as predicted by basic thermodynamics. This alternate theory will be considered in relation to recent experiments on the subject. [ABSTRACT FROM AUTHOR]

Considering the exciton effect, the excitation energy and its binding energy of the metallic single-walled carbon nanotubes (SWNTs) are theoretically studied by using the simple tight-binding model, based on which the linear absorption spectra are also calculated. It is found that due to the trigonal warping effect, the excitation energies of the linear optical spectra all are split into two corresponding ones. Additionally, the splitting depends on both the chirality and the transition energy: (1) the splitting is maximal for the zigzag tubes, the splitting decreases with the increasing chiral angle; (2) the higher the transition energy is, the larger the splitting is. It is very interesting to find that the obtained results are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]