Simultaneously improve the Purcell factor and internal quantum efficiency of light-emitting diodes via surface plasmon by metal conic structure

Abstract

Recent advances in the development of surface plasmons (SPs) enhanced LED have provided a great opportunity to enhance either the internal quantum efficiency (IQE) or the spontaneous emission rate (SE) by employing specific metal structures. However, it is still challenging to simultaneously achieve high IQE and Purcell factor (Fp), which demonstrates the SE enhancement, without sacrificing the electrical performance of LEDs. Herein, we designed and investigated a conic metal structure applied to LEDs by comprehensively considering the electrical, optical, and data transmission performance of devices. Conic structures with various heights were implemented to investigate the variation trends of IQE and Fp with the structure design, accompanied by the planar structures as references. A more than five times increase in IQE and almost five times increase in Fp were demonstrated experimentally even with a coupling distance of 100 nm, by employing this conic structure. The theoretical analysis was verified by the experimental results and revealed the mechanism of high Fp and IQE toward high SP–photon coupling efficiency and initial IQE. This study provides a universal strategy to enhance the performance of luminous efficiency and modulation speed of LEDs without sacrificing electrical properties, making them viable for the integration of lighting, display, and communication.