A scintillator composition of a halide perovskite material of at least one ABX.sub.3 type halide perovskite, at least one activator for the matrix material and optionally at least one charge compensator to assist the incorporation of the activator in the perovskite lattice and any reaction products thereof. Radiation detectors that use the scintillators are also described, as are related methods for detecting high-energy radiation and method of producing an activated halide-perovskite based scintillator crystal.