Facile and Dynamic Color-Tuning Approach for Organic Light-Emitting Diodes Using Anisotropic Filters

Organic light-emitting diodes (OLEDs) typically have broad emission spectra, and tuning of OLED emission is often required for use in displays, lighting, and biomedical applications. In this study, we investigate a facile and dynamic color-tuning approach for the fine-tuning of OLED emission by using the anisotropic property of squaraine dye as an external thin film filter. We compared the results of the proposed tuning method with conventional methods of emission tuning, using the microcavity effect and varying emissive layer thickness. Our experiments and optical simulations show that the anisotropic filtering effect, caused by graded absorption of the squaraine layer, effectively removes the tail emission at longer wavelengths and has the highest range of color tuning as compared to the conventional methods. Our results demonstrate the potential of anisotropic filters as a simple alternative method for OLED emission tuning.