Quantum Dynamical Approach to Predicting the Optical Pumping Threshold for Lasing in Organic Materials

We present a quantum dynamic study on organic lasing phenomena, which is a challenging issue in organic optoelectronics. Previously, phenomenological method has achieved success in describing experimental observation. However, it cannot directly bridge the laser threshold with molecular electronic structure parameters and cavity parameters. Quantum dynamics method for describing organic lasing and obtaining laser threshold is highly expected. In this Letter, we first propose a microscopic model suitable for describing the lasing dynamics of organic molecular system and we apply the time-dependent wave-packet diffusion (TDWPD) to reveal the microscopic quantum dynamical process for the optical pumped lasing behavior. Lasing threshold is obtained from the onset of output as a function of optical input pumping. We predict that the lasing threshold has an optimal value as function of the cavity volume and depends linearly on the intracavity photon leakage rate. The structure-property relationships between molecular electronic structure parameters (including the energy of molecular excited state, the transition dipole and the organization energy) and the laser threshold obtained through numerical calculations are in qualitative agreement the experimental results, which also confirms the reliability of our approach. This work is beneficial to understanding the mechanism of organic laser and optimizing the design of organic laser materials. TO

General Approach To Compute Phosphorescent OLED Efficiency

Phosphorescent organic light-emitting diodes (PhOLEDs) are widely used in the display industry. In PhOLEDs, cyclometalated Ir(III) complexes are the most widespread triplet emitter dopants to attain red, e.g., Ir(piq)3 (piq = 1-phenylisoquinoline), and green, e.g., Ir(ppy)3 (ppy = 2-phenylpyridine), emissions, whereas obtaining operative deep-blue emitters is still one of the major challenges. When designing new emitters, two main characteristics besides colors should be targeted: high photostability and large photoluminescence efficiencies. To date, these are very often optimized experimentally in a trial-and-error manner. Instead, accurate predictive tools would be highly desirable. In this contribution, we present a general approach for computing the photoluminescence lifetimes and efficiencies of Ir(III) complexes by considering all possible competing excited-state deactivation processes and importantly explicitly including the strongly temperature-dependent ones. This approach is based on the combination of state-of-the-art quantum chemical calculations and excited-state decay rate formalism with kinetic modeling, which is shown to be an efficient and reliable approach for a broad palette of Ir(III) complexes, i.e., from yellow/orange to deep-blue emitters

Improved fuzzy logic method to distinguish between meteorological and non-meteorological echoes using C-band polarimetric radar data

To obtain better performance of meteorological applications, it is necessary to distinguish radar echoes from meteorological and non-meteorological targets. After a comprehensive analysis of the computational efficiency and radar system characteristics, we propose a fuzzy logic method that is similar to the MetSignal algorithm; the performance of this method is improved significantly in weak-signal regions where polarimetric variables are severely affected by noise. In addition, post-processing is adjusted to prevent anomalous propagation at a far range from being misclassified as meteorological echo. Moreover, an additional fuzzy logic echo classifier is incorporated into post-processing to suppress misclassification in the melting layer. An independent test set is selected to evaluate algorithm performance, and the statistical results show an improvement in the algorithm performance, especially with respect to the classification of meteorological echoes in weak-signal regions