Photoluminescence and Electroluminescence from a Hybrid of Lumogen Red in Nanoporous-Silica

Abstract

In this paper white electroluminescence from a lumogen red-doped nanoporous silica matrix is presented. The matrix was prepared using a sol-gel process, and lumogen red--a perylene derivative--was doped at a number of concentrations. The photoluminescence and electroluminescence of the lumogen red-doped nanoporous-silica composite were investigated in detail. The structures, surface morphology, and optical properties of the nanoporous silica composites were investigated. The average pore size of the nanoporous-silica matrix was approximately 5 nm. The absorption spectra of the lumogen red in the nanoporous-silica matrix were broader than those from solution specimens. The photoluminescence of the lumogen red-doped nanoporous-silica matrix depended strongly on the excitation wavelengths. When excited at relatively longer wavelengths, e.g., 467 nm, the emissions peaked at constant positions (approximately 608 nm) for all cases, except a small shift to the red from its solution 601 nm. However, if excited at a shorter wavelength in the range of 200-400 nm, additional blue emissions were observed, which were particularly strong and suggested defect centers of the nanoporous-silica matrix. The electroluminescence from a single-layered sandwich device consisting of the lumogen red-doped nanoporous-silica was interesting. When driving with an AC electric field, electroluminescence spectra covered a whole spectral range, consisting of the red emission from lumogen red and the blue and green emission from the nanoporous silica matrix. In this way, we actually achieved a white electroluminescence from this hybrid organic and silica device with a color coordinate, CIE [x, y] = [0.30, 0.35] at a driving electric field of 3.0 x 10(6) V/cm. This was a first attempt to investigate electroluminescence from an organic dye-doped nanoporous silica matrix.