CsPbI ₃ Nanoplatelets for Stable and Efficient Bright-Red Light-Emitting Diodes

Metal halide perovskite (CsPbX 3, X = Cl, Br, I) nanoplatelets (NPLs) have emerged as promising materials for lighting and display applications, owing to their tunable photoluminescence (PL) wavelength over the visible spectrum and ultranarrow full width at half-maximum (fwhm). However, precise control over the thickness of CsPbI 3 NPLs to achieve bright-red emission (620–635 nm) with a narrow fwhm remains a significant challenge for high-definition display applications. In this work, bright-red-emitting CsPbI 3 NPLs with four [PbI 6 ] 4– octahedron layers are synthesized by incorporating 4-dodecylbenzenesulfonic acid (4-DBSA) as a ligand via the hot-injection method with some modifications. The 4-DBSA-CsPbI 3 NPLs were further post-treated with n -tetrabutylammonium iodide (TBAI), resulting in bright-red-emitting 4-DBSA/TBAI-CsPbI 3 NPLs with a high photoluminescence quantum yield (PLQY) of 98%, a narrow fwhm of 26 nm, and improved colloidal stability. The PL intensity of the 4-DBSA/TBAI-CsPbI 3 NPL colloidal solution retains 91% of its initial value after 20 days of storage at room temperature. A bright-red lighting-emitting diodes (LEDs) fabricated using these CsPbI 3 NPLs demonstrated an high excellent external quantum efficiency (EQE) of 11.8%, a brightness of 2396 cd/m 2, and a narrow electroluminescence fwhm (27 nm) at 625 nm.