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Keywords:

  • 68.65.La;
  • 71.35.−y;
  • 73.21.Hb;
  • 78.60.Fi;
  • 78.67.Lt;
  • 85.60.Jb

Abstract

We will discuss our experimental results for optical spectra produced by hole-injection from different p-type organic and inorganic materials into n-type ZnO nanowires. The influence of different growth techniques and conditions on the nanowires and their emission spectral characteristics will then be analyzed and discussed. The latest findings on the mixture of the green emission band responsible for visible light emission from ZnO and the blue light emission from the organic polymer will be presented. Different high brightness light emitting diodes (HB-LEDs) from our grown ZnO nanowires are demonstrated. The p-type multi layer organic structures contain PEDOT:PSS as hole injectors combined with a hole transporting layer, and in some structures, a final top electron blocking/hole barrier stepping layer is placed. The purpose of this layer is to adjust the hole and electron emission from the corresponding junction side to optimize the LED performance. Structural scanning electron microscopy (SEM), electrical (IV characteristics), photoluminescence (PL) and electroluminescence (EL) characteristics of these devices are displayed. Theoretically, we study the superfluidity of a two-dimensional system of excitonic polaritons in an optical microcavity with an embedded quantum well. Using the effective low-energy action for thermodynamic phase fluctuations, we obtain an expression for the analogue of the superfluid density in the system in terms of the “current–current” correlation function. The Kosterlits–Thouless transition temperature to the superfluid state as a function of the controlling parameters is calculated. Two methods are considered for producing traps for a polariton system in an optical microcavity. The behaviour of a two-component Bose condensate of photons and excitons is analyzed theoretically for both types of the trap. The Bose condensate is described by the coupled system of equations of the Gross–Pitaevskii type. The approximate wave functions and the spatial profiles of coupled photon and exciton condensates are obtained. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)