Multicolor Organic Single‐Crystal Microcavity Light Emitting Diodes With High Color‐Purity and High Brightness

Abstract The development of ultra‐high‐definition (UHD) displays demands organic light‐emitting diodes (OLEDs) with high color purity of all three primary colors for a wide color gamut and high brightness essential for future AR/VR applications. However, the vibronic coupling in organic emitters typically results in broad emissions, with a full width at half maximum (FWHM) exceeding 40–50 nm. Herein, multicolor organic single‐crystal microcavity light‐emitting diodes (SC‐MC‐OLEDs) are demonstrated by embedding ultrathin 2D organic single crystals (2D‐OSCs) between two silver layers that serve as both electrodes and mirrors. By leveraging the microcavity effect, the resonant output frequencies of SC‐MC‐OLEDs can be continuously tuned from 448 to 602 nm by adjusting the thickness of 2D‐OSCs (i.e., the microcavity length), achieving high color purity with a full width at half maximum (FWHM) of <10 nm. Furthermore, the Purcell effect in SC‐MC‐OLEDs enhances the radiative rate and improves light‐coupling efficiency, resulting in a maximum external quantum efficiency (EQE) of up to 4% and minimal efficiency roll‐off. Due to the excellent bipolar transport properties of OSCs, the brightness of SC‐MC‐OLEDs surpasses 10 6 cd m −2 , along with a degree of linear polarization exceeding 0.9, unlocking new application opportunities.