Light-Emitting Devices Attaining Theoretical Outcoupling Efficiency Exceeding 60% via Scattering Particles

The high efficiency of the light-emitting devices is pivotal for its successful application in any lighting system. Nevertheless, most of luminous devices grapple with the challenge of suboptimal luminous efficiency due to the notably low light extraction efficiency (LEE) even the internal quantum efficiency (IQE) can reach 100%. In this study, we have deeply investigated the impact of the dense scattering layer with particle-embedded (DSL) on the LEE of light-emitting devices theoretically and experimentally. The particle concentration in DSL is so high that the effective refractive index of the film layer can be tuned by varying the concentration. Therefore, in addition to the scatterance S, asymmetry factor g, and absorption coefficient k, the effective refractive index has also been emphasized. According to theoretical calculation, an LEE of 62% can be achieved by placing DSL between the substrate (Sub) and electrode in the organic light-emitting diode (OLED). The internal waveguide (WG) and Sub modes are effectively extracted by optimizing the key parameters of DSL. The bottom emissive OLED based on DSL achieves 12.8% external quantum efficiency (EQE), roughly 1.91 times higher than the reference device, which is consistent with the simulation results. The findings may promote light-emitting diode (LED) devices to reach over 60% LEE levels and provide practical guidance for device implementation.