Study Of White Organic Light-emitting Devices Using Color Conversion Films

A novel white organic light-emitting device (WOLED) which using a strategy of exciting color conversion film with a blue organic light-emitting diode, is currently attracting considerable attention for its potential applications as full color display, backlights for liquid crystal displays and solid state lighting. The color conversion film WOLED (CCF-WOLED) would have a attractive future of commercialization for their advantages of simple fabricating technic, high brightness, long lifetime and high color stability.Our works mainly focus on the fabrication of CCF-WOLEDs and enhancement of the electroluminenscence(EL) performance as follows:Firstly, by employing a high efficiency fluorescent dye N-BDAVBi doping into the host of CBP as blue emitter, a blue OLED has been fabricated successfully with a configuration of ITO/NPB/CBP:N-BDAVBi/BPhen/LiF/Al. The color conversion film is prepared by dispersing a red fluorescent pigment VQ-D25 into the epoxy resin. By optimizing the thickness and fluorescent pigment doping concentration of the CCF, A good EL performance of the CCF-WOLED has been achived with the CIE coordinates of (0.32, 0.29) at the driving voltage of 9V, the maximum current efficiency of 3.2cd/A at 4.35mA/cm~2, the maximum brightness of 7600 cd/m~2 at the operating voltage of 14V. Meanwhile we also study influence on the device EL performance related to the pigment doping concentration and the thickness of CCF.Secondly, blue OLED combined the CCF using another salmon pigment VQ-D24 has also been fabricated, and we have achieved a high color stability in the CCF-WOLED with a good EL performance. When the driving voltages varies between (from) 7 V to 14 V, the color coordinates (CIE) changes slightly from (0.33, 0.32) to (0.34, 0.28), and the maximum current efficiency is about 7.3cd/A at 4.35mA/cm~2, the maximum brightness is 12000 cd/m~2 at the operating voltage of 14V. Then we gave an explanation of the dissimilar EL performance in these WOLEDs with different CCF's pigments.Thirdly, the organic/inorganic color conversion film is prepared by dispersing a mixture of red pigment VQ-D25 with YAG phosphor into PMMA. A novel WOLED has been successfully achieved with the high color stability by optimizing the thickness and pigment concentration of the multiplex color conversion film. When the driving voltage changes from 6 V to 14 V, the color coordinates (CIE) varies slightly from (0.354, 0.304) to (0.357, 0.312) and the maximum brightness is 16800 cd/m~2 at the operating voltage of 14 V, compared with the current efficiency of 3.2cd/A in the WOLED with red VQ-D25 and the current efficiency of 4.25cd/A in the WOLED with inorganic YAG phosphor, we achieve the maximum current efficiency is about 5.8 cd/A at 4.35mA/cm~2, Ultimately we study the mechamism of the performance improvement for the WOLED with YAG phosphor in CCF. Finally, we have made the summary and expectation of the study on CCF-WOLED.