A sensitive and robust thin-film x-ray detector using 2D layered perovskite diodes

Abstract

Solid-state radiation detectors, using crystalline semiconductors to convert radiation photons to electrical charges, outperform other technologies with high detectivity and sensitivity. Here, we demonstrate a thin-film x-ray detector comprised with highly crystalline two-dimensional Ruddlesden-Popper phase layered perovskites fabricated in a fully depleted p-i-n architecture. It shows high diode resistivity of 10¹² ohm·cm in reverse-bias regime leading to a high x-ray detecting sensitivity up to 0.276 C Gy_air ^-1 cm^-3. Such high signal is collected by the built-in potential underpinning operation of primary photocurrent device with robust operation. The detectors generate substantial x-ray photon-induced open-circuit voltages that offer an alternative detecting mechanism. Our findings suggest a new generation of x-ray detectors based on low-cost layered perovskite thin films for future x-ray imaging technologies.

Fig. 1. Thin-film x-ray detectors and their properties.

(A) Schematic illustration of the 2D RP–based p-i-n thin-film x-ray detector device architecture composed of (BA)₂(MA)₂Pb₃I₁₀ (dubbed as Pb3) as an absorbing layer. (B) GIWAXS map of the 2D RP thin film done under synchrotron beam. (C) Calculated linear x-ray absorption coefficient (μ_l) as a function of incident radiation energy for hybrid perovskite materials and silicon. (D) J-V characteristic for 2D RP and silicon reference devices in the dark and under x-ray (10.91 keV) exposure. (E) X-ray–generated charge density as a function of x-ray dosage for 2D RP (red) and silicon diode (black) under zero bias. (F) X-ray–induced charge density subtracted by the dark noise (signal-to-noise ratio) for 2D RP and silicon reference detector from (E).

Fig. 2. Device characteristics.

(A) Power-dependent J-V characteristics for 2D RP thin-film x-ray detector response with Pb3 as an absorbing layer (470-nm thickness) under various photon fluxes. (B) On-current at various reverse biases as a function of photon flux in unit of counts per second (Ct s⁻¹) for the 2D RP device. (C) Capacitance-voltage curve for the 2D RP thin-film device (470 nm). The capacitance is normalized by its capacitance at 0 bias. Open-circuit voltage (V_OC) as a function of normalized x-ray beam flux in log scale for different energy values of (D) 10.91 keV and (E) 8.05 keV for 2D RP (470 nm) and silicon reference devices. (F) Photo emission spectra of the Pb3 thin-film device excited by hard x-ray (red) as compared to the photoluminescence spectra of the Pb3 thin film (green) and the Pb3 single crystal (blue) excited by laser (405 nm). a.u., arbitrary units.

Fig. 3. Devices’ temporal responses and stabilities.

(A) Transient photocurrent response of device with various applied resistance. (B) Time-resolved photo conductivity of a thin-film device under pulsed-laser excitation (375 nm). (C) Device signal fall time extracted from (B) under various biases. (D) Stability test of the thin-film detector operating under continuous hard x-ray (10.91 keV) exposure under short circuit conditions.