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Organic Light Emitting Diode Material Process and Devices Part 6

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Tham khảo tài liệu 'organic light emitting diode material process and devices part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 116 Organic Light Emitting Diode - Material Process and Devices PHOLEDs is very broad and hole trapping is not so severe. The EL emission spectra of devices D E and F are shown in Fig. 12 a and CIE coordinates in Fig. 12 b . Wavelength nm Fig. 10. Normalized electroluminescent spectra of devices A B and C at the luminance of 1000 cd m2. Thickness  Device D Device E Device F X nm 0 10 20 Bebq2 Ir piq 3 100 100 100 Bebq2 400 300 200 Table 6. Recombination zone position in Device C from the HTL EML interface 2.3 eV 2.7 eV 2.8 eV St 3.1 eV Ti lr piq 3 100 -5 j eV F X nm Bebq2 5.5 eV 5.5 eV - Bebq2 500  Fig. 11. Recombination zone position in Device C High Efficiency Red Phosphorescent Organic Light-Emitting Diodes with Simple Structure 117 Fig. 12. a EL emission spectra and b CIE coordinates of devices D E and F. 4.2 Conclusions A narrow band-gap host material Bebq2 for red PHOLEDs with a very small exchange energy value of 0.2 eV between singlet and triplet states has been demonstrated. It shows almost no barrier to injection of charge carriers and charge trapping issue in PHOLEDs is minimized. High current and power efficiency values of 9.66 cd A and 6.90 lm W in bilayered simple structure PHOLEDs are obtained respectively. The operating voltage of bilayered PHOLEDs at a luminance of 1000 cd m2 was 4.5 V. In conclusion simple bilayerd red emitting device with Bebq2 host could be a promising way to achieve efficient economical and ease manufacturing process important for display and lighting production. 5. Single layer structure 5.1 Introduction Organic light emitting devices OLEDs have made significant stride Pfeiffer et al. 2002 and the technology has already been commercialized to mobile flat panel display applications. Thermal evaporation technique and complicated fabrication process consisting of multiple layers for charge carriers balancing and exciton confinement Baldo and Forrest 2002 Coushi et al. 2004 Tanaka et al. 2007 are employed in highly efficient .