Synergistic role of hydrogen bonding and band degeneracy leads to enhanced X-ray detection in HPIP-(NH4)0.7Cs0.3Br3·H2O perovskites

Abstract

Metal-free perovskites (MFPs) have emerged as a promising material for the development of eco-friendly, non-toxic, and wearable X-ray detectors. However, the advancement of MFPs has been hindered by several significant challenges, most notably their lower absorption coefficient and susceptibility to oxidation and degradation in iodine-based detectors. To address these issues, this study proposes a novel approach involving the doping of the B-site with Cs ions. The incorporation of Cs ions prompts degeneracy in the lowest unoccupied molecular orbital (LUMO) while preserving the dominant hydrogen bonds within the structure. As a result, there is an enhancement of several physical properties, including an increase in ion migration activation energy, augmentation in X-ray absorption capacity, and an improvement in the migration rate-lifetime (μτ) product. These enhancements are facilitated by the synergistic effects of multiple factors. Ultimately, when compared with detectors based on a single B-site ion (NH₄⁺ and Cs⁺), the X-ray detector based on the HPIP-(NH₄)_0.7Cs₀.₃Br₃·H₂O single crystal demonstrates a two-fold increase in sensitivity, achieving 1661 μC Gy_air⁻¹ cm⁻², and a detection limit of 402 nGy_air⁻¹ s⁻¹. This study validates the effectiveness of the B-site Cs ion doping strategy, paving the way for the development of high-performance devices in related fields.