High‐Degree Organic–Inorganic Disorder Enables Near‐Unity Photoluminescence Quantum Yield and Robust High‐Pressure Luminescence in Manganese Halides

Abstract The development of novel luminescent materials that simultaneously optimize emission efficiency and extreme environment robustness remains imperative yet challenging. By employing growth interface engineering, Bmpip 2 MnBr 4 (Bmpip + or PP14 + = N‐butyl‐N‐methylpiperidinium) featuring high organic–inorganic multiple disorder is synthesized. Whereas structural disorder typically leads to performance degradation, this multiple‐disorder significantly suppresses configuration distortion and motion freedom within the zero‐dimensional (0D) [MnBr 4 ] 2− that occurs in its isomer. Combined with strong quantum confinement induced by the large Mn‐Mn separation, Bmpip 2 MnBr 4 unexpectedly achieves a near‐unity photoluminescence quantum yields (PLQY) ‐ surpassing that of [PP14] 2 [MnBr 4 ] (PLQY = 55%). High‐pressure investigations further demonstrate the superiority of this high‐degree multiple‐disorder design: Bmpip 2 MnBr 4 shows unprecedented photoluminescence robustness up to 22.5 GPa, with a remarkable emission enhancement of 16‐fold at 6.9 GPa. In stark contrast, 0D configuration distorted [PP14] 2 [MnBr 4 ] shows pressure‐suppressed emission and quenches below 15.2 GPa. Mechanistically, the stabilization of 0D units, along with the response of crystal field splitting and optical absorption cross‐section under high pressure, governs the modulation of PL properties at both ambient and high‐pressure conditions. Besides, another fully‐ordered compound 1‐mpip 2 MnBr 4 also be reported, which exhibits a lower PLQY and undergoes pressure‐induced dimerization at 1.6 GPa. This work establishes multiple‐disorder engineering as an effective strategy for constructing high‐performance luminescent structures.