Analysis of Electronic Structure and Optical Properties in Mq3(M=Al, Ga) as Emitting Materials for OLEDs

• Main Authors: Chen, Tsung-Kai, 陳琮凱
• Other Authors: Hong, Che-Wun
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/14332731731439019522

碩士 === 國立清華大學 === 動力機械工程學系 === 99 === This thesis employs a quantum simulation technique to analyze how the materials that are used to fabricate the emitting layer affect the electronic and photonic properties of the final product - an organic light emitting diode (OLED). The materials of interest that are used to fabricate the emitting layer in OLEDs are Mq3, Mq2p (M=Al, Ga) and their “CH”/N (i.e., replace the C-H bonds in both qa and qc with N atoms) derivatives. he first step before the quantum simulation takes place is to set-up meridional-Mq3 molecular models which included Mq2p and its “CH”/N substitution derivatives. Both time-independent and time-dependent density functional theory (TI-DFT and TD-DFT, respectively) techniques are employed. The former is used to optimize the molecular structures, and the latter to determine the electronic excitation energy. Then, the ground state structures to calculate the bond length, bond angle, dipole moment, band gap, molecular orbital, ionization energy, electron affinity, reorganization energy, were optimized using the DFT. The corresponding UV/VIS spectrum and absorption/excitation energies are evaluated from the TD-DFT technique. With the resulting fluorescence spectrum, the Stokes shift can be observed. Quantum simulations were carried out with the Gaussian09 software package which makes use of the hybrid exchange-correlation functional B3LYP and the 6-31g(d), 3-21g* basis sets. Finally, simulation results and experimental data were compared for both Alq3 and Gaq3 derivatives. It was concluded that Gaq3 derivatives displayed a better performance than the Alq3 derivatives. It is hoped that with the fundamental academic design tool provided here, future investigations on the performance of novel materials for fabricating OLEDs can be continued.