利用激基复合物发光的有机白光电致发光器件

以NPB为空穴传输材料,(dppy)BF为发光层,Alq为电子传输层和色度调节层,制备了有机白光电致发光器件.该器件的白光发射是来自于(dppy)BF与NPB的固界表面形成的激基复合物发光,以及NPB与(dppy)BF发射的蓝光.该白光器件的色度稳定,在电压10～25V的变化范围内,色坐标变化由(0.29,0.33)到(0.31,0.35).器件在4V开启,12V电压下亮度和效率分别为200cd/m²和0.45lm/W.

White Light Emission from Exciplex

Electroluminescent devices based on organic semiconductors have gained a great deal of attention because of their high luminance,low drive voltage,and variety of emission colors.Different applications have different demands on the emitted light;sometimes colors are needed and in other cases it is necessary to have a bright white light source,especially for backlight applications in liquid crystal displays.Organic white light emitting diodes(LEDs)based on electroluminescent organic molecules have been reported using the microcavity technique,multilayer structures,multiple-quantum wells structures,or polymer LED based on polymer blends.However,most of the methods have the drawback that the chromaticity of emission coulor changes largely with the operating voltage,or the fabrication processes are more complex.We demonstrate efficient organic white light-emitting devices(LEDs),using N,N-diphenyl-N,N'-bis(1-naphthyl)-(1,1-biphenyl)-4,4'-diamine(NPB)as hole-transporting layer,1,6-bis(2-hydroxyphenyl)pyridine boron complex((dppy)BF)as emitting layer,tris-(8-hydroxyquinoline)aluminum(Alq)as electron-transporting and chromaticity-tuning layer.This type of device has a simpler structure than those mentioned above,thus the fabrication process is much simpler.The white light comes from exciplex emission at the solid-state interface between(dppy)BF and NPB and from the exciton emission of NPB and(dppy)BF layers respectively.The chromaticity of white emission can be tuned by adjusting the thickness of Alq layer.The white LEDs with the Alq thickness of 15nm exhibit a maximum luminescence of 2 000cd/m² and efficiency of 0.58 lm/W,and the Commission Internationale De L'Eclairage(CIE)coordinates of resulting emission vary from(x=0.29,y=0.33)to(x=0.31,y=0.35)with increasing forward bias from 10V to 25V.The region is very close to equienergy white point(x=0.33,y=0.33).