有机发光器件的一种失效机制

An Invalidation Mechanism in Organic Light-Emitting Diodes

制备了结构为铟锡氧化物(ITO)/NPB/插入层/Alq/LiF/Al的有机电致发光(EL)器件,测量了器件发光随电压变化的光谱和电压-电流-亮度特性,观察到这种结构器件在电压升高的过程中总是在某电压附近有一个光谱、亮度和效率等性能突变的不可逆过程,这是由于在发光区域附近的纳米薄层材料将导致电荷在该区域的局部聚集,并引起该薄层材料局部破坏。这一失效的机制表明,尽管在器件制备过程中可能需要在器件中使用几纳米厚的有机层,但是应当考虑尽量避免,以使器件内载流子分布合理,避免此类失效过程发生。

Organic light-emitting diodes （OLEDs） with the structure of indium-tin-oxide （ITO）/NPB/inserting layer/Alq/LiF/A1 have been fabricated. The electroluminescence （EL） spectra of devices with different driving voltage and the characteristics of voltage-current-luminance have been measured. It has been observed that an irreversible process on the EL performance, such as luminescence spectra, bright, efficiency, begin to occur instantly if the voltage increase to some value. The related mechanism has been analyzed. The nanometer-thick inserting layer near the recombination zone may lead to local accumulation of carriers or charges, and result in a local breakage or phase transition of the inserting thin layer. This study shows that a nanometer-thick organic layer should not be used in OLED for preventing this invalidation process.