Enhanced X-ray detection of one-dimensional DABCO–NH4I3 perovskites via anisotropic carrier transmission study

Metal-free perovskites exhibit significant potential for wearable X-ray detectors due to their non-toxic nature, degradability, aqueous solution processability and superior optoelectronic properties. DABCO–NH₄I₃ (DABCO denoted as N,N′-diazabicyclo[2.2.2]octonium) is a promising metal-free perovskite due to its advantages of reduced exciton binding energy, enhanced mobility–lifetime product and superior absorption coefficients. However, the undesirable X-ray detection performance of the device restricts its application. Reducing the dimensions of perovskite materials and adjusting the crystal orientation are effective methods for improving optoelectronic properties and enhancing detection performance. Herein, a high quality one-dimensional DABCO–NH₄I₃ single crystal is synthesized and in contrast to the conventional X-ray photoconductivity fitting approach, the time-of-flight (TOF) method using alpha particle-induced pulses is first employed to study the differences in single carrier transport performance between the [001] and [010] directions. The fitting results show that the hole mobility–lifetime products (μτ) for the [001] and [010] directions are 1.1 × 10⁻³ cm² V⁻¹ and 2.9 × 10⁻⁴ cm² V⁻¹ and hole mobilities (μ) are 55.53 cm² V⁻¹ s⁻¹ and 4.63 cm² V⁻¹ s⁻¹, respectively. Furthermore, the X-ray response results demonstrate a higher sensitivity of 62.1 μC Gy⁻¹ cm⁻² with a lower detection limit of 0.16 μGy s⁻¹ for the [001] direction at 70 V (a sensitivity of 9.2 μC Gy⁻¹ cm⁻² with a detection limit of 0.16 μGy s⁻¹ for the [010] direction). Hence, enhanced performances are successfully obtained by investigating the transport anisotropy of the DABCO–NH₄I₃ perovskite which also provides a feasible route to improving the detection performance of metal-free perovskites and promoting its applications.