A metal-free molecular pyroelectric material with strong pyro-photovoltaic coupling for enhancing self-powered X-ray response†

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 the pyro-photovoltaic coupling effect. Interestingly, benefiting from the molecule-level modification, the pyroelectric-active candidate CY–I exhibits a high pyroelectric coefficient P_e 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 enables a significant improvement in the photocurrent (∼158.5%), facilitating superior self-powered X-ray detection, including sensitivity (88 μC Gy⁻¹ cm⁻²) and a low detection limit (137 nGy s⁻¹). This work provides an effective solution to enhance the X-ray response performance in metal-free materials and offers new insights into the development of environmentally friendly, self-powered broadband detectors.