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制备了结构为ITO/CuPc/NPB/Alq_3/LiF/Al的常规有机发光二极管,之后对器件采用波长为442 nm和325 nm的激光线进行照射产生激子,并在小偏压下(保证器件没有开启)对激子的演化过程进行控制,同时测量器件的光致磁电导(photo-induced magneto-conductance,PIMC).实验发现,不同于电注入产生激子的磁电导效应,PIMC在正、反小偏压下表现出明显不同的磁响应结果.当给器件加上正向小偏压时,器件的PIMC在0—40mT范围内迅速上升;随着磁场的进一步增大,该PIMC增加缓慢,并逐渐趋于饱和.反向小偏压时,器件的PIMC随着磁场也是先迅速增大(0—40 mT),但达到最大值后却又逐渐减小.通过分析外加磁场对器件光生载流子微观过程的影响,采用‘电子-空穴对’模型和超精细相互作用理论对正向偏压下的PIMC进行了解释;反向偏压下因各有机层的能级关系,为激子与电荷相互作用提供了必要条件,运用三重态激子与电荷的反应机制可以解释PIMC出现高场下降的实验现象.
Conventional organic light-emitting diodes of the structure ITO / CuPc / NPB / Alq 3 / LiF / Al were prepared and then irradiated with laser lines of 442 nm and 325 nm wavelength to generate excitons. Under small bias voltage Not on) to control the evolution of excitons and measure the photo-induced magneto-conductance (PIMC) of the device.It is found that, unlike the magneto-conductance effect of excitons generated by electrical injection, The results show obviously different magnetic response under anti-small bias.When the device is biased with positive bias, the PIMC of the device increases rapidly in the range of 0-40mT. As the magnetic field increases, the PIMC increases slowly , And gradually become saturated.When the reverse bias is small, the device’s PIMC increases rapidly with the magnetic field (0-40 mT), but decreases gradually after reaching the maximum value.After analyzing the applied magnetic field, The influence of the carrier microcosmic process is explained by using the ’electron-hole pair’ model and the theory of hyperfine interaction for explaining PIMC under forward bias. Due to the energy level relationship of each organic layer under reverse bias, Exciton and charge interactions provide the necessary conditions, the use of triple The reaction mechanism of state exciton and charge can explain the experimental phenomenon that PIMC appears high field decrease.