Recently, Associate Researcher Liu Feilong's team, led by Professor Zhou Guofu at the South China Advanced Optoelectronics Research Institute of South China Normal University, utilized three-dimensional dynamic Monte Carlo simulations to uncover the physical mechanism behind devices. The findings were published in Physical Review Applied and highlighted on the journal's homepage by the editors.
Understanding the operational principles of optoelectronic devices holds significant scientific importance for applications such as novel displays and semiconductors. Taking organic light-emitting diodes (OLEDs) as an example, comprehending their fundamental device physics is crucial for further material design, optimization, and efficiency enhancement. Experimental evidence has demonstrated a significant improvement in device current density by diluting certain disordered organic semiconductors. However, analyzing the dilution effect experimentally may be hindered by various complex phenomena, such as the formation of phase-separated regions and the impact of dilution on energy disorder. So far, a comprehensive physical theory explaining this phenomenon has not been elucidated.
Liu Feilong's team employed three-dimensional dynamic Monte Carlo simulations to systematically investigate the impact of inert material dilution on the current density in single-polarity sandwich-type disordered organic semiconductor devices. Unlike traditional semiconductor physics theories, diluting disordered organic materials with inert materials enhances their current-voltage characteristics due to the "trap dilution" effect. They systematically studied its intrinsic physical mechanism. Simulation results confirmed that this effect is caused by the previously proposed trap dilution and demonstrated when the increase in current density due to trap dilution exceeds the negative effects of dilution-induced mobility reduction.
The study further examined the sensitivity to dilution level, layer thickness, measurement conditions (voltage and temperature), and average hopping distance (by altering the electron wave function decay length), and proposed an original analytical physical model that well-described the results of the three-dimensional simulations, consistent with experimental findings. These discoveries elucidate the device physics mechanism and can be utilized for designing more optimized optoelectronic and semiconductor devices.
Related paper information: https://doi.org/10.1103/PhysRevApplied.21.014050
