激基复合物器件的光电流和光致发光磁效应

The magnetic effects of photocurrent and photoluminescence in exciplex-based devices

本文制备了一系列不同浓度、厚度和禁带宽度的激基复合物光电器件,在325 nm激光照射下,测量了不同偏压和温度下器件的光电流磁效应(Magneto-photocurrent, MPC)和光致发光磁效应(Magneto-photoluminescence,MPL).实验发现,在不同温度下,尽管器件的MPC和MPL线型均表现为ISC (Intersystem Crossing, ISC)过程主导的指纹式响应曲线,但其偏压依赖关系却完全不同,即MPC幅值随外加负偏压的增加而减小,随外加正偏压的增加先增加后减小;而MPL幅值与外加偏压无关.此外,随着浓度的增加, MPC幅值逐渐减弱, MPL幅值先增大后减小;随着厚度的增加, MPC幅值减小, MPL幅值保持不变.另外, MPC幅值在禁带宽度较小的激基复合物器件中表现更大.分析认为, MPC幅值变化是由器件中ISC过程与激子的解离和传输作用共同决定,而界面处激子的辐射与ISC过程的竞争则会影响MPL幅值的变化.该工作对理解光激发下激基复合物器件的微观机制具有一定的参考价值.

A series of exciplex-based devices with different doping concentrations,thicknesses and bandgaps have been fabricated in this paper,and their magneto-photocurrent(MPC)and magneto-photoluminescence(MPL)at different bias voltages and temperatures have been measured under 325 nm laser excitation.Experimental results show that although both MPC and MPL curves show the fingerprint-like line shape dominated by the intersystem crossing(ISC)process at various temperatures,their bias dependences are completely different.The value of MPC decreases with increasing the reverse bias,and increases first and then decreases with increasing the forward bias.But the value of MPL is independent on the applied bias.In addition,the value of MPC gradually decreases with increasing the concentration or thickness,but the value of MPL increases first and then decreases with increasing the concentration and is independent on thickness.What’s more,the value of MPC for the exciplex-based devices with a small band gap is large.By analyzing the structure,spectra and energy level distribution of exciplex-based devices,we conclude that the change for the magnitude of MPC is determined by the dissociation,transport and ISC processes of exciton in the devices,and the amplitude of MPL is governed by the radiation and ISC processes of exciton at the interface.This work will provide a reference for understanding the microscopic mechanisms in the exciplex-based devices under photoexcitation.