Deep-blue hybrid perovskite light emitting diode with high color purity based on CH₃NH₃PbCl₃

CH₃NH₃PbCl₃ (MAPbCl₃) light emitting diodes (LEDs) with emission in deep-blue were demonstrated with an areal dimension of 3.5 mm by 3.5 mm. An inverted p-i-n diode structure consisted of ITO/PEDOT:PSS/MAPbCl₃/TPBi/LiF/Al with bulk MAPbCl₃ thin film as the emission layer was synthesized via combined thermal deposition, spin-coating, and anti-solvent treatment techniques. The perovskite film was authenticated by X-ray diffraction, scanning electron microscopy, and atom force microscopy and exhibited high in crystallinity and morphology. The energy level alignments between layers were determined by the UPS technique. The device displayed a diode behavior with a turn-on voltage of approximately 3.2 V and a saturation current density of 118 mA/cm². Under forward bias, the emission of LEDs was centered at 408.8 nm with a full width at half maximum of only 7 nm, a color purity of 97% and an CIE coordinate of (0.16, 0.036), respectively. The optimum external quantum efficiency and luminance of 0.036% and 37 cd/m² were achieved at current density of approximately 90 mA/cm² and 118 mA/cm² at room temperature, respectively. To our best knowledge, this investigation first realized bulk perovskite LEDs with the shortest emission wavelength and the highest color purity in deep-blue.