利用多阱结构改善有机电致发光器件效率

将N,N'-bis-(1-naphthy1)-N,N'-dipheny-1,1'bipheny1 4,4'-diamine(NPB)与bathocuproine(BCP)2种材料以交叠沉积方式组成一种周期性结构作为空穴注入层,制备了结构为ITO/[NPB/BCP]n/AlQ/LiF/Al的有机电致发光器件(OLED).通过改变空穴注入层阱状结构的重复周期数n,可改变载流子复合区域,进而获得近白光和绿光发射.由于该结构能获得更好的载流子注入平衡,具有交叠结构空穴注入层的近白光器件在15 V时亮度达到3 433.8 cd/m2,在电流密度为60.9 mA/cm2时最大发光效率为2.26 cd/A.当周期数n大于3时得到绿光发射,与单空穴注入层ITO/NPB/AlQ/LiF/Al器件相比,交叠空穴注入层可将器件的最大亮度由2 512.8 cd/m2提高到866 1.0 cd/m2,最大亮度效率在20 mA/cm2时达到4.94 cd/A.

The Luminance Efficiency Improvement of Organic Light Emitting Diode Using Multiple-quantum-well Structure

Organic light-emitting diodes(OLEDs)with multiple-quantum-well structures,which consist of acromatic diamine and bathocuproine have been fabricated.The structure of the device is ITO/[NPB/BCP]n/AlQ/LiF/Al.The effect of the multiple-quantum-well(MQW)structure on the performance of OLEDs with tris(8-hydroxyquinoline)aluminum as the emitting material has been investigated.The emitting zone can be changed with the number of MQW.The maximum brightness of white emitting device reaches 3 433.8 cd/m2.The luminous efficiency is 2.26 cd/A at the current density of 60.9 mA/cm2.The brightness of the diode with the MQW number of 5 has been reached 866 1.0 cd/m2 with respect to 2 512.8 cd/m2 of the conventional green emitting diode without the MQW structure(ITO/NPB/AlQ/LiF/Al).The highest luminous efficiency is 4.94 cd/A at the current density of 20 mA/cm2.Such an improvement in the device performance should be attributed to the improved hole-electron balance,which can be further attributed to the introduction of the MQW structure.