Revealing the main limiting factors of modulation bandwidth in quantum dot light-emitting diodes through an electro-optical coupled modulation model

Quantum dot light-emitting diodes (QLEDs) are promising for light sources in visible light communications due to their solution-processability and chip integration capability. The equivalent circuit model is a typical method to analyze modulation bandwidth for QLEDs, but it only describes electrical behavior, failing to quantify electro-optical conversion, and hindering the identification of the main factors limiting modulation bandwidth of QLEDs. This serious issue prevents further improvement of QLED modulation bandwidth under theoretical guidance. This study proposes an electro-optical coupled model integrating electro-optical conversion (equated to a low-pass filter) into the equivalent circuit. The model reflects comprehensive physical processes, shows high consistency with experimental results. We identify the electroluminescence decay time as the main bottleneck limiting the bandwidth. Targeted optimizations significantly improve modulation bandwidth from 1.57 to 8.04 MHz, providing actionable guidelines for QLEDs with high modulation bandwidth.