Centimeter-Scale Violet Light Emitting Diode with Two-Dimensional BA₂PbBr₄ Perovskite Emitter

Two-dimensional (2D) perovskite light emitting diodes (LEDs) with violet emission were demonstrated with areal sizes in the centimeter scale. High-quality and uniform 2D BA₂PbBr₄ thin film was synthesized via combined thermal evaporation, spin-coating, and anti-solvent techniques. The perovskite film was authenticated by X-ray diffraction, scanning electron microscopy, and atomic force microscopy and exhibited high in crystallinity and morphology. The absorption spectrum fitted using Tauc plot revealed a bandgap of ∼3.0 eV, which agrees well with the photoluminescence spectrum. A p-i-n diode structure with a BA₂PbBr₄ active area of ∼2 cm² was fabricated using LiF, TmPyPb, and PEDOT:PSS as the electron injection, electron, and hole transport layers, respectively. The device displayed a diode behavior with a turn-on voltage at 1.75 V and a saturation current of 65 mA cm⁻². The electroluminescence of LEDs was centered at ∼406 nm with full width at half maximum of 13.6 nm, a color purity of 83.9%, and CIE coordinates of (0.18, 0.07). The optimum external quantum efficiency and luminance of 0.083% and 112 cd m⁻² were achieved at current density of 59 mA cm⁻². To our best knowledge, this investigation first realized 2D BA₂PbBr₄ perovskite LEDs with the shortest emission wavelength and high color purity in violet.