A Metal-free Molecular Pyroelectric Material with Strong Pyro-Photovoltaic Coupling for Enhancing Self-Powered X-ray Response

Abstract

Metal-free X-ray detectors have shown enormous application potential in the fields of public safety and medical diagnostics, owing to their environmentally sustainable and low-cost characteristics. However, the X-ray absorption and response capabilities of metal-free materials are constrained by their intrinsic low atomic number and low density. Here, we have constructed a series of metal-free pyroelectric materials, CY-X (CY = cyclohexylamine, X= Cl, Br, and I), showing remarkable X-ray detection responses enabled by pyro-photovoltaic coupling effect. Interestingly, benefiting from the molecule-level modification, the pyroelectric-active candidate CY-I exhibits a high pyroelectric coefficient Pe of ~35 × 10-4 μC cm-2 K-1 and demonstrates an exceptional photo-pyroelectric effect across a broad spectrum, covering the range from X-ray to 266-980 nm. Such X-ray-response pyro-photovoltaic coupling behavior achieves a significant improvement of the photocurrent (~158.5%), facilitating the superior self-powered X-ray detection, including outstanding sensitivity (96 μC Gy⁻1 cm⁻2) and low detection limit (137 nGy s⁻1). This work provides an effective solution to promote the X-ray response in metal-free materials and offers new insight into the development of environmentally friendly, self-powered broadband detectors.