Solution‐Processed Mn‐Doped 2d Perovskite Wavelength Shifters for Noble‐Liquid Photon Detection

ABSTRACT Several large particle physics experiments rely on scintillation light emitted by liquefied noble gases to detect ionizing radiation. This vacuum‐ultraviolet light is commonly converted to visible light by wavelength‐shifting coatings on photon detectors. Materials combining a large Stokes shift, scalable large‐area fabrication, and cryogenic robustness remain limited. Here we demonstrate solution‐processed Mn‐doped PEA 2 PbBr 4 thin films as a wavelength shifter for liquid Ar scintillation readout. Mn incorporation converts the native excitonic emission into a Mn 2+ emission band centered at ∼620 nm, providing a large Stokes shift that suppresses reabsorption and shifts the emission to the region of maximum SiPM sensitivity. Cryogenic operation is supported by temperature‐dependent photoluminescence, showing a ∼70% increase in integrated emission at 80K, with preserved film morphology after repeated liquid‐nitrogen thermal shocks and no measurable photobleaching under intense 337 nm pulsed irradiation. Under 265 nm excitation, the Mn‐doped films deliver an effective photon conversion efficiency of (100 ± 20)% (λ em ≈ 620 nm), lower than state‐of‐the‐art TPB reference films ((150 ± 10)%, λ em ≈ 420 nm). Despite this, PEA 2 PbBr 4 offers scalable large‐area solution processing and superior cryogenic morphological stability compared with TPB, supporting its potential as a wavelength shifter for cryogenic scintillation detection.