Cesium Lead Bromide (CsPbBr₃) Thin‐Film‐Based Solid‐State Neutron Detector Developed by a Solution‐Free Sublimation Process

Abstract

Besides its high stability, CsPbBr 3 possesses interesting electronic and optoelectronic properties such as high attenuation above the band gap, good photoresponse, large electron and hole mobility, long lifetimes, low excitation binding energy, halogen self-passivation, defect tolerance, luminosity, etc. [1,4-11] Device-quality single crystals have been prepared using a number of methods including a high-temperature process, [4] solution-based methods such as antisolvent vapor crystallization (AVC), [7,8,10] and inverse temperature crystallization. [12] The carrier concentration (holes) of these crystals varies in the range of 5 × 10 7 to 1 × 10 8 cm −3[9,10] and about 1 × 10 9 cm −3 for electrons, [9] resulting in nearly intrinsic crystals with resistivities in the range of 1-3 GΩ cm. [10] As a reference, Bridgmangrown crystals show resistivities as high as ≈340 GΩ cm [4,13] and mobility-lifetime (μτ) product for electrons and holes in the range of 1.7 × 10 −3 to 4.5 × 10 −4 cm 2 V −1 and 1.3 × 10 −3 to 9.5 × 10 −4 cm 2 V −1 , respectively. [4,14,15] These μτ values are better than that of CdZnTe (CZT) and CdTe. It is important to note that the electron μτ product of CZT and CdTe [4,11] is in the lower range of the corresponding values for CsPbBr 3 while the hole μτ product is only 0.1% that of CsPbBr 3. [4] The reported use of CsPbBr 3 for radiation sensing is limited to single crystals, except for its use as a thin film in X-ray scintillators. [1,3] There are no reports for direct radiation detection using thin-film diodes based on CsPbBr 3. This is related to the lack of deposition techniques for thick CsPbBr 3 films. The close space sublimation (CSS) process reported here addresses this problem. Although the intrinsic phase purity and crystal quality of single crystals offer improved optoelectronic properties, the high cost of the single crystal approach renders this option nonviable for portable and large-area applications, hence thin films are a better option. Furthermore, the photon attenuation coefficient of CsPbBr 3 is linear and comparable to that of CZT for energies up to 1000 keV, [4] but no exhaustive studies exist for the interaction of CsPbBr 3 with charged particles (α, β, etc.) or for higher photon energies such as gamma rays. The interaction of CsPbBr 3 2D nanosheets with ionizing radiation has been reported recently showing scintillation performance comparable to commercial crystals. [1] The observed The majority of solid-state radiation sensors are predominantly single crystals. However, for low-cost and large-area device applications, thin films are a better option. The first evidence of neutron detection using a Gallium Oxide/Cesium Lead Bromide (Ga 2 O 3 /CsPbBr 3) solid-state diode enabled by an innovative close space sublimation (CSS) method that allows deposition of thick CsPbBr 3 films is demonstrated. Furthermore, indirect neutron sensing is achieved using a 10 B layer for diodes biased at voltages as low as-5 V, showing the potential for low-power operation. The neutron response is ...

3D Microstructured Inorganic Perovskite Materials for Thermal Neutron Detection

“…Finally, Au contacts were deposited by e‐beam on top of the perovskite to serve as the anode. The detailed process for the perovskite deposition step was demonstrated elsewhere by the group [ 30 ] as well as the ion‐exchange treatment. [ 31 ] A thin layer of metallic chromium was deposited on the perovskite layer to serve as the hard mask for microstructure etching.…”

“…The detailed experimental methods for the fabrication of planar CsPbBr 3 ‐based detectors are reported in ref. [ 30 ] . Figure 1b shows the schematic cross‐section of microstructured CsPbBr 3 ‐based detectors used in this work to increase detection efficiency.…”

“…To challenge such limitations, close spaced sublimation (CSS) method was recently proposed as an alternative to grow stoichiometric films with controllable thickness from sublimated CsPbBr 3 crystals. [ 30 ] ; Moreover, CSS allows to modulate film composition trough an ion‐exchange recrystallization treatment that results in an enhancement of their transport characteristics. [ 31 ] The resulting planar thin‐film CsPbBr 3 /Ga 2 O 3 ‐based, p–n junction diodes, coupled with 10 B neutron conversion film, have been demonstrated previously by our group showing a thermal neutron detection efficiency of 2.5%.…”

“…[ 31 ] The resulting planar thin‐film CsPbBr 3 /Ga 2 O 3 ‐based, p–n junction diodes, coupled with 10 B neutron conversion film, have been demonstrated previously by our group showing a thermal neutron detection efficiency of 2.5%. [ 30 ] with low voltage operation and high gamma discrimination. Our simulation results show that the theoretical thermal neutron detection efficiency of planar detectors coupled with a 10 B conversion layer is limited to ≈4.5%.…”

“…In this paper, we built upon our previously reported thin‐film planar detectors to demonstrate high thermal neutron detection efficiency using microstructured thin‐film CsPbBr 3 ‐based diodes. [ 30 ] We patterned trenches of up to 10 μm deep into the CsPbBr 3 layer via a HBr and Ar plasma dry etching process to then backfill them with 10 B using a sedimentation process designed to prevent any damage to the perovskite layer. The fabricated microstructured CsPbBr 3 thermal neutron detectors show a detection efficiency of 4.3%.…”