NPB和TPBi作为间隔层调控OLED激子复合区域

Manipulation of exciton recombination zone in organic light-emitting diodes by utilizing NPB or TPBi as a spacer

以ITO/MoO_3/NPB/Ir(ppy)_3/TPBi/Cs_2CO_3/Al器件为基础,采用NPB和TPBi作为间隔层(spacer)制备了器件ITO/MoO_3/NPB/Ir(ppy)_3/NPB(spacer)/TPBi/Cs_2CO_3/Al和ITO/MoO_3/NPB/TPBi(spacer)/Ir(ppy)_3/TPBi/Cs_2CO_3/Al,并通过调节间隔层厚度、分析器件的电致发光(EL)光谱,研究其对激子复合区域的调控。实验结果表明,所有器件的激子复合区域均位于NPB和Ir(ppy)_3,且复合区域随电压的增大和间隔层的增厚向NPB移动。NPB(spacer)的厚从0nm增至10nm,色坐标均匀变化,总变化值Δ(x,y)<(0.02,0.10);而TPBi(spacer)对应的色坐标变化量Δ(x,y)<(0.04,0.20),厚≤6nm时,光谱变化较小(即调节幅度较小),而10nm时光谱变化较大。这表明,通过调节间隔层材料或者厚度,就能简单、方便地调控激子复合区域,为不同复合区域发光强度的粗调/微调和白光器件的设计提供依据。

In this work,based on the fundamental device of ITO/MoO3/NPB/Ir（ppy）3/TPBi/Cs2CO3/Al,devices with structures of ITO/MoO3/NPB/Ir（ppy）3/NPB（spacer）/TPBi/Cs2CO3/Al and ITO/MoO3/NPB/TPBi（spacer）/ Ir（ppy）3/TPBi/Cs2CO3/Al were fabricated.The effect of the spacer thickness on exciton recombination zone is investigated by analyzing electroluminescent （EL） spectra.The experimental resu lts indicate that the exciton recombination zone of all devices are located in NPB and Ir（ppy）3.The recombin ation zone shifts towards NPB with the increase of the applied voltage and spacer thickness.As the thickness of NPB spacer increases from 0nm to 10nm,Commission Internationale de L′Eclairage （CIE） coordinates are equably ch anged,and its variation,Δ（x,y） is less than （0.02,0.10） .For the devices with TPBi as a spacer,Δ（x,y）〈（0.04,0.20）.When the thickness of TPBi spacer is no more than 6nm,the evolution of spec tra with the thickness is negligible,which leads to narrow adjustment range.Whe n the thickness of TPBi spacer is 10nm,the shift of spectra is greater.That is, it is a simple and convenient approach for changing the spacer and its thickness to manipulate the exciton recombination zone.This provides a guidance for the rough or fine tuning of emission intensity from dif ferent zones and the design of white organic light-emitting diodes （OLEDs）.