Color‐Pure and Stable Amber Perovskite Quantum Dot Films With Dramatically Enhanced Light Extraction

The amber gap, where amber light exhibits the lowest emission efficiency, critically limits the high performance of white light‐emitting diodes (WLEDs) and display technologies. Here, we demonstrate color‐pure and stable amber perovskite quantum dot (APQD) composite films to overcome the amber gap issue. The orthorhombic APQDs, synthesized via anion exchange under ambient conditions, exhibit a high photoluminescence quantum yield (PLQY) of 84%. The APQD thin films have a narrow emission band with a full width at half maximum (FWHM) of 16 nm. These APQDs suffer from light trapping due to refractive index mismatch. Incorporating hexagonal boron nitride (h‐BN) scattering particles within APQD/polymethyl methacrylate (PMMA) films redirects the trapped waveguide mode, achieving a remarkable 14.1‐fold enhancement in light extraction. The composite film maintains 85% luminescence intensity after 4 months under ambient conditions. This study presents a promising approach for developing high‐performance solid‐state lighting solutions for amber light with improved efficiency and stability.