论文标题
统一的动态方法，用于模拟金属/有机界面处的量子隧道和热发射器
Unified dynamic approach for simulating quantum tunneling and thermionic emission at metal/organic interface
论文作者
论文摘要
金属电极的注入是有机半导体设备中电荷产生的主要渠道，通常认为量子效应是必不可少的。我们基于表面跳跃（SH）算法和经典设备建模开发动态方法，通过该算法和经典设备建模，通过该算法以及在金属/有机接口处的电荷载体注入的量子隧道和热发射发射。观察到来自金属电极的注射电荷通过接近内置电场引起的界面接近界面的积累，迅速扩散到有机分子上，表现出从离域化到定位的过渡。我们通过模拟电荷注入动力学的温度依赖性来比较平均场水平和SH算法的Ehrenfest动力学，并且发现前者会导致不当结果，即在室温下，随着温度的升高，注射效率降低，而室温则是可信度的。注射电荷与所施加的偏置电压之间的关系表明，量子隧道主导了分子晶体中低阈值的注入特性，这进一步得到了注射过程中小熵变化的计算结果。还量化了界面电荷注入效率的最佳界面宽度，并且可以用来了解界面缓冲层在实际设备中的作用。
Injection from metallic electrodes serves as a main channel of charge generation in organic semiconducting devices and the quantum effect is normally regarded to be essential. We develop a dynamic approach based upon the surface hopping (SH) algorithm and classical device modeling, by which both quantum tunneling and thermionic emission of charge carrier injection at metal/organic interfaces are concurrently investigated. The injected charges from metallic electrode are observed to quickly spread onto the organic molecules following by an accumulation close to the interface induced by the built-in electric field, exhibiting a transition from delocalization to localization. We compare the Ehrenfest dynamics on mean-field level and the SH algorithm by simulating the temperature dependence of charge injection dynamics, and it is found that the former one leads to an improper result that the injection efficiency decreases with increasing temperature at room-temperature regime while SH results are credible. The relationship between injected charges and the applied bias voltage suggests it is the quantum tunneling that dominates the low-threshold injection characteristics in molecular crystals, which is further supported by the calculation results of small entropy change during the injection processes. An optimum interfacial width for charge injection efficiency at the interface is also quantified and can be utilized to understand the role of interfacial buffer layer in practical devices.
