Yellow‐Emitting Organic–Inorganic Hybrid Manganese Halides Realized by Br/Cl Composition Engineering

Abstract Organic–inorganic hybrid manganese halides (OIHMH) represent a novel class of emerging luminescent materials that hold significant promise for light‐emitting diode (LED), X‐ray imaging, and ferroelectric technologies. However, the OIHMH materials report to date predominantly emit green and red light, which is constrained by the Mn coordination geometry in tetrahedral or octahedral environments, thereby limiting their versatility in various applications. In this study, the emission spectrum of OIHMH is successfully extended to include yellow light by manipulating structural alterations through Br/Cl composition engineering. A series of BTA 2 MnBr 4‐ x Cl x (BTA: C 10 H 16 N, x = 0–4) phosphors exhibit an abrupt transition in luminescence color from green to yellow at x = 2.5. Counterintuitively, changes in the crystal field strength caused by the substitution of Cl for Br do not affect the emission wavelength. Instead, it is the structural modifications induced by the Cl‐for‐Br substitution that are responsible for the yellow luminescence. To demonstrate the benefits of this yellow emission, we have realized a white LED device using a single BTA 2 MnCl 4 yellow phosphor, an achievement that is not feasible with the previously reported green or red‐emitting OIHMH materials. This paper extends the yellow emission capability to OIHMH materials, thereby unlocking new avenues for application.