Interface Energy-Level Reorganization for Efficient Perovskite γ-Ray Detectors.

Metal halide perovskites are promising candidates for gamma-ray (γ-ray) spectrum detectors. However, achieving high-resolution energy spectra in single-photon pulse-height analysis mode remains challenging, due to the inevitable leakage currents degrade the recognizable fingerprint energies which is critical for resolving γ-ray spectroscopy. We demonstrate under high bias voltage, a deficient contact barrier can lead to excessive surface charge injection, thereby increasing leakage current from electrodes to perovskites. Hence, we conceive to employ surface ligand engineering on perovskite single crystals to manipulate energy levels to suppress leakage current. In particular, anchoring a strong dipole ligand onto the perovskite induced surface charge-density displacement, leading to a downward band bending and heightened the corresponding contact barrier. Consequently, the strategy minimized the detectors' leakage current by an order of magnitude, to as low as 44 nA cm at -100 V. The resulting detectors show a significant improvement in energy resolution, 3.9 % for Na 511 keV γ-rays has been achieved at room temperature. The resulting detector further resolves each fingerprint energy for Eu γ-spectrum, representing one of the best γ-rays perovskite detectors reported to date. Moreover, the detectors exhibited stabilized energy resolution without any degradation under a continuous electric field (1,000 V cm) for over 300 minutes, representing the longest longevity reported to date.