Lighting Hidden Traces: Rapid Green Synthesis of Zero‐Dimensional Manganese Halide Perovskite for X‐Ray and Fingerprint Imaging

ABSTRACT Lead‐free, eco‐friendly organic–inorganic manganese halides (OIMnHs) have attracted considerable attention for optoelectronic applications, owing to their outstanding optical properties and facile solution processability. Here, we present a novel zero‐dimensional (0D) OIMnH, (BrEtPPh 3 ) 2 MnBr 4 , synthesized as centimeter‐sized single crystals (SCs) under ambient conditions. Additionally, we developed a rapid (<2 min) green “shake‐and‐make” synthesis method to directly obtain its powder form, named direct synthesized powder (DSP). Both SCs and DSP display strong green emission, with high photoluminescence quantum yields (PLQYs) of 51.28% for SCs and 88.68% for DSP, as well as exceptional color purity and photochemical stability. Flexible scintillator films, fabricated by blending PMMA with either SC or DSP, enable high‐resolution X‐ray imaging (5 lp/mm) and the imaging of diverse objects. Notably, DSP demonstrates a high light yield (∼117k photons/MeV), rivalling commercial and other Mn‐based SC scintillators, and stands as the first lead‐free, flexible perovskite scintillator made directly from powder. Furthermore, DSP facilitates efficient, sensitive, and background‐free latent fingerprint detection, offering clear ridge detail, the resolution of levels 1–3 features, and strong contrast across various surfaces, even after aging. This study marks the first such demonstration for OIMnHs, underscoring a simple, eco‐friendly approach to multifunctional materials for X‐ray scintillation and forensic latent fingerprint detection.