Alternating current (AC) driven light emitting devices (LEDs) are recently dragging attention due to its efficient color tunability. These devices consist of multilayer structure as the direct current (DC) driven LEDs, but the multilayer structure has drawbacks such as the large amount of material usage that increases the fabrication cost, and the difficult yield control due to a number of processing steps. In contrast, a recently demonstrated AC driven LED with a single contact has several advantages compared to the previous structures such as simple device structure, diverse emissive dye materials, and efficient charge injection.
Here we introduce a method to efficiently tune the color of an LED, by varying the AC voltage frequency of the LED comprising a single contact structure. This simple device structure enables an efficient charge injection without any additional functional layers, while showing efficient color tunability with the emissive layer comprising mixed dyes. This is done by controlling the exciton population via varying the frequency of the AC voltage, while limiting the number of the lowest energy dye molecules, thus being able to observe a dramatic spectral shift from the low energy dye emission to the higher energy depending on the AC frequency.
Project ended: 03/09/2023