Excitons in organic molecular crystals

Optical Properties of Perylene Thin Films on Cu(110)

“…Our biexponential fitting of the integrated fluorescence intensity as a function of sample temperature is shown in Figure D, which gives activation barriers of 15.6 and 100.0 meV, respectively. This is similar to those found in PTCDA (21.2 and 131.5 meV) films …”

“…As the temperature increases, the lifetime of the excimer decreases which results in the increase of peak width and the decrease of peak intensity. For this type of thermal quenching of total luminescence intensity, a biexponential expression of fluorescence intensity as a function of temperature was recently discussed for crystalline PTCDA and Cl 4 MePTCDI films, similar to the inorganic semiconductors. The biexponential function is the result of two activation processes.…”

Study of excited states in thin films of perylene derivatives by photoluminescence and absorption spectroscopy

“…The pure perylene source material was purchased from Aldrich Chemical Co. and used as received. Thin layers of the investigated materials were prepared by the thermal evaporation method (details of the sample preparation given in [8,9]). Solutions of the investigated materials were prepared by dissolving purified powder in ethanol via sonication.…”

“…Solutions of the investigated materials were prepared by dissolving purified powder in ethanol via sonication. The photoluminescence (PL) and absorption spectra were measured using the experimental setup described in [8,9].…”

Optical investigation of L-leucine L-leucinium picrate

“…The best refinement gives E a = 10.82 meV and E b = 66.07 meV. It was found that the PL thermal quenching is mainly caused by the carriers escape from the excited state to the exciton state connected with the defect center, and phonon-exciton interactions provide a nonradiative transition path, leading to the luminescence quenching at higher temperatures which is typical for organic molecular crystals [29]. Moreover, the peak position shows a significant red shift with the increase of temperature, of approximately 32 meV which can be caused by the localization of the carriers at low temperatures [30].…”