空穴阻挡层BCP对掺杂型有机发光二极管中磁电导效应的影响

Influence of BCP hole blocking layer on magnetoconductance effect in dye doped organic light emitting diodes

通过在器件复合发光区附近插入空穴阻挡层BCP,制备了一种具有非平衡传输性能的荧光染料掺杂型发光二极管,其结构为ITO/CuPc/NPB/NPB:DCM(5wt%)/BCP/Alq3/LiF/Al,并在不同温度和电压下测量了器件的注入电流随外加磁场的变化(即磁电导效应).实验结果表现为:当磁场处在0～40mT时,该非平衡发光器件的磁电导随磁场的增加而迅速增大(即表现为快变的正磁电导效应).这一实验现象与具有相对平衡传输性能的发光器件中所观测到的磁电导效应一致;当磁场大于40mT时,非平衡发光器件的磁电导随磁场的进一步增加表现为缓慢下降(即缓变的负磁电导效应成分),而平衡器件的磁电导则变为继续缓慢增加(即为缓变的正磁电导效应).本文对非平衡传输掺杂型发光器件的体系特征进行了讨论,并基于三重态激子-电荷(T-Q)反应受外加磁场的影响对上述实验现象进行了定性解释.

Dye doped organic light emitting diodes with unbalanced carriers transport property have been fabricated through inserting a hole blocking layer near the recombination emission area. The device structure is ITO/CuPc/NPB/NPB： DCM（5 wt%）/BCP/Alq3/LiF/A1. The magnetic field effects on current （magnetoconductance, MC） were studied under different bias voltages and temperatures. Results show that the MC of the unbalanced device increases sharply with the magnetic field in low-field range （0≤B≤40 mT）, which is similar to the MC response of the balanced transport device. Compared to the high field saturation in MC of the balanced device, MC of the unbalanced device turns to decrease at magnetic field strength larger than 40 mT. The characteristics of the doped fluorescent device with unbalanced carders transport property are discussed in this study, and a mechanism based on the magnetic field modulated triplet-charge interaction is proposed to explain qualitatively the observed results.