The thermoluminescence (TL) exhibited by crystalline tris(2-phenylpyridine) iridium (Ir(ppy)(3)) microrods was investigated over temperatures of 29-160 degrees C using a multichannel Fourier transform spectrometer. The glow curves and TL spectra were analyzed to elucidate the origins of the emission. Four peaks were observed at different temperatures in the glow curves. Furthermore, by analyzing the TL spectra, we found that various types of charge-carrier trap sites exist in Ir(ppy)(3); these sites become active or remain inactive, depending on the presence of oxygen or light or both. Thus, charge-carrier trapping within crystalline Ir(ppy)(3) depends on the environment to which the sample has been exposed. (C) 2014 Elsevier B.V. All rights reserved.