Luminescence of CuBr and Its Correlation to the Exciton

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Abstract
Luminescence and photoconductivity spectra in evaporated films or polycrystals of CuBr have been studied. Relationship between the emission and absorption spectra, leads to the conclusion that the resonance emission is due to the annihilation of an intrinsic exciton of the lowest energy. An emission line similar to I 1 in CuCl and other narrow emission lines are found. These are considered to arise from bound excitons. Equidistant structure is observed in emission spectra of some films as well as in an excitation spectrum of the resonance emission. The energy difference between the peaks in the structure is equal to the transversal optical phonon energy. On the basis of various experimental results, a radiative annihilation process of an intrinsic exciton is discussed. From the photoconductivity spectrum, the band gap energy is estimated to be 3.02 eV at 8°K. The thermal activation energy for the dissociation of the lowest energy exciton is obtained as 0.10±0.02 eV from the resonance emission intensity vs. 1/T curve.