Optical and x–ray scintillation properties of X₂MnCl₄ (X = PEA, PPA) perovskite crystals

An emerging prospect of solution-processed organic–inorganic hybrid halide perovskites is promising for next generation x-ray imaging applications. Herein, the optical and x-ray scintillation properties of lead-free two-dimensional perovskite crystals are reported, i.e. X₂MnCl₄ (X = PEA, PPA). At room temperature (RT), the photoluminescence (PL) spectra of both crystals show a peak around 600 nm with the lifetime between 3 and 4 µs, making them applicable for scintillator in x-ray imaging applications. Materials with a small electronic band gap of about 2 eV may allow a good promise for high-light-yield scintillators. On the other hand, x-ray luminescence (XL) measurements for both crystals show no spectra at RT, while those at 10 K exhibit the similar features observed in PL spectra. Temperature-dependent XL intensities reveal thermal quenching behaviour with activation energies between 40 and 54 meV. Thermoluminescence (TL) and glow curves in both crystals show residual luminescence background as slow as 1648 s and some deep traps with energies as large as 190 meV. Thermal quenching and TL measurements of both crystals are the opposite of those of PEA₂PbCl₄ crystals. Although some properties may not be beneficial for scintillators, the small differences of scintillation properties in both crystals may provide direction for the new designs of high-light-yield lead-free perovskite single crystal scintillators. (paper)