The investigation of the luminescent structure of thallium-doped cesium iodide (CsI:Tl) basing on the first-principles coupled with spectral analysis.

The luminescent structure of thallium-doped cesium iodide (CsI:Tl) and the behavior of electrons during luminescence are studied at great length based on the conventional first-principles calculation combined with ordinary spectroscopic analysis befittingly in this work. The hybrid functionals based on a screened Coulomb potential (HSE) is used to visualize the energy band structure of the experimental sample's system, and the corresponding relationship between the transition behavior of CsI:Tl energy levels and the spectrum is studied more accurately. We show the complete energy conversion process clearly, which involves the crystal beginning to receive the energy of a photon until the moment of de-excitation. All the fluorescence process is completed by Tl+ions that replace Cs+ions. Our results verify and complement the previous theories and potentially provide important references for the adjustment and design of the detectors and imaging equipment in different fields.

[Spectral analysis of organic/microcavity organic light-emitting devices with the change in thickness of organic layer].

Organic light-emitting devices (OLEDs) with emission peak at 520 nm were designed. The electroluminescence (EL) spectra including the integrated intensity, the peak width at half height, and the intensity and the position of the peak of the EL spectra of the OLEDs and microcavity OLEDs (MOLEDs), the total thickness of organic layers which is changeable, were calculated and theoretically analyzed with the thickness of the layer of NPB and light-emitting layer of Alq3 ranging from 10 to 100 nm, respectively. According to these studies, it was found that the optimized OLEDs should be constructed with 70 nm NPB and 62 nm Alq3, and this structure should be more suitable to configurate the MOLEDs. These results suggest that the suitable structure of OLEDs/MOLEDs could be designed with help of theoretical calculation, which is also helpful to the light-emitting properties of OLEDs and MOLEDs.

[Simulation of microcavity organic light emitting device with two kinds of resonant cavity lengths].

The resonant cavity length of microcavity influences the light emitting characteristics of microcavity organic light emitting device (MOLED) directly. According to the related calculation formula of microcavity device, when the lengths of microcavity are lambda/2 and lambda, the authors use transfer matrix method to simulate and compare with the functions of composite light emitting EL when exciton is in different positions of microcavity. The authors found that when the length of microcavity is lambda/2, the peaks of luminous spectrum are all at the 520 nm, and the width of half-peaks are all 17 nm. The peak intensity and integral intensity are biggest when exciton is in the central area of microcavity. When the length of microcavity is lambda and exciton is at different positions of microcavity, the peaks of luminous spectrum are all at the 520 nm of designed center wavelength, and the widths of half-peaks are all 12 nm. The peak intensity and integral intensity are smallest when exciton is in the central area of microcavity. After analyzing, The authors found that the light emitting characteristics is best when the exciton is at the maximum position of the electric field. This is because the electric field's intensities in the microcavity with two kinds of lengths are distributed differently. It illustrates that one should distinguish different resonant cavity length and exciton at the maximum position of the electric field within microcavity if one wants to create an efficient MOLED.