Efficiency improvement of organic light-emitting diodes device by attaching microlens arrays and dependencies on the aspect ratio

Computational simulation study of multilayer organic light-emitting devices (OLED) is performed by attaching a microlens array on the top of the glass substrate facing the air to suppress waveguiding loss. We analyzed the influence of aspect ratio and height of microlens array on the optical characteristics. The results reveal that a hexagonal packing type device exhibits the 35% EQE at a 103 lm/m² brightness level. With minimum roll-off in EQE, 30% occurs at the brightness level of 105 lm/m². Besides, a broad spectrum is observed with a slight shoulder band around 650 nm in the electroluminescence emission curve. The Commission International de l'Eclairage (CIE) color coordinates of OLED with microlens arrays are much different from that without microlens arrays. Thus, it affects the chroma quality of the OLED devices and is more sensitive with microlens arrays in the viewing angle range. In addition, we also demonstrated the variation of outcoupled efficiency as a function of ETL–TPBi thickness over different polarization modes. Our results indicate that the device extracted more light with a microlens array and provided better device fabrication results. (author)