Understanding the type, formation energy and capture cross section of defects is one of the challenges in the field of organometallic halide perovskite (OMHP) devices. Currently, such understanding is limited, restricting the power conversion efficiencies of OMHP solar cells from reaching their Shockley–Queisser limit. In more mature semiconductors like Si, the knowledge of defects is one of the major factors in successful technological implementation. This knowledge and its control can make a paradigm shift in the development of OMHP devices. Here, we report on deep level (DL) defects and their effect on the free charge transport properties of the single crystalline methylammonium lead bromide (MAPbBr₃) perovskite. To determine DL activation energy and capture cross section, we used photo-Hall effect spectroscopy (PHES) with enhanced illumination in both steady-state and dynamic regimes. This method has shown to be convenient due to the direct DL visualization by sub-bandgap photo-excitation of trapped carriers. DLs with activation energies of E_V + 1.05 eV, E_V + 1.5 eV, and E_V + 1.9 eV (or E_C − 1.9 eV) were detected. The hole capture cross section of σ_h = 4 × 10⁻¹⁷ cm² is found using photoconductivity relaxation after sub-bandgap photo-excitation. Here, our experimental results demonstrate the existence of DL defects responsible for non-radiative recombination and their positions inside the bandgap for the first time. Additionally, the transport properties of single crystal MAPbBr₃ are investigated by Time of Flight (ToF) measurements at several biases. These measurements further confirm the increase of Hall mobility and the enhancement of hole transport produced by sub-bandgap illumination in MAPbBr₃ devices. The analysis of charge carrier transport by ToF measurements in combination with the energy of DLs identified by PHES can explain the long hole carrier lifetime in MAPbBr₃ devices, while the electron carrier lifetime is largely affected by trap-assisted recombination. Here, our studies provide strong evidence for deep levels in OMHPs and open a richer picture of the role and properties of deep levels in MAPbBr₃ single crystals as a system model for the first time. The deeper knowledge of the electronic structure of OMHPs could open further opportunities in the development of more feasible technologies. Indeed, knowledge of the exact positions of DLs is beneficial in controlling these defects by crystal growth modification to eliminate these defects as was done for classical inorganic semiconductors, for example, in Si, GaAs, and CdTe development.

Organometallic halide perovskite (OMHPs) single crystals have recently gained attention for high-energy radiation detection due to their low trap state densities, high bulk resistivities, excellent stopping power and cost-effective solution growth. An integral focus for radiation sensing materials is the reduction of trap states to enhance charge transport properties. In this perspective, we investigate the use of high and low purity precursors for growth to understand impurity inclusion, as well as effects on structural properties due to impurities. Using both high purity and low purity precursors, we report minimal effects on impurity inclusion observed via Raman, ToF-SIMS and X-ray diffraction. Through SEM analysis, we observe that the particle size in the grown single crystal increased on average by a factor of two to five, when using high purity precursors. The microstructural changes affect the recombination mechanisms, promoting longer charge carrier lifetimes (τ_avg), where time-resolved photoluminescence shows a large increase from τ_avg = 1.26 × 10⁻⁶ s (low purity) to τ_avg = 1.18 × 10⁻⁴ s (high purity). We further investigate the purity effects with alpha radiation detection, demonstrating charge collection efficiency and observing an increase in charge collection by 32 ± 30% using the higher purity precursors. The microstructural differences in growth are herein proposed to be caused by nucleation from the impurities present in the solution, thereby adversely affecting the electronic properties of the MAPbBr₃ single crystals. In this perspective, we provide a deeper understanding of the effects of precursor purity on solution-based single crystal growth of OMHPs towards development of efficient radiation sensors and optoelectronic devices.

Monte Carlo simulations have been used for calculating the energy deposition of beta particles in the depletion region of a silicon carbide (SiC) betavoltaic cell along with the corresponding theoretical efficiencies. Three Monte Carlo codes were used in the study: GEANT4, PENELOPE, and MCNPX. These codes were used to examine the transportation of beta particles from 90Y, 90Sr, and 35S. Both the average beta energy from each source and the entire spectrum were modeled for calculating maximum theoretical energy deposition in both a spherical and slab geometry. A simulated depletion region was added in postprocessing containing the maximum energy deposited per micrometer. The calculated maximum efficiencies with the slab configuration model are approximately 1.95%, 0.30%, and 0.025% using monoenergetic average energy and 1.54%, 0.25%, and 0.019% using an energy spectrum for 35S, 90Sr, and 90Y, respectively. These efficiencies when using the spherical configuration model are 2.02%, 0.31%, and 0.023% using th...

We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 $\mathsf{\mu }\mathrm{m}$ pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than $0.1$ MeV), and a third group of samples with 200 MeV pions, in steps, to ($8.8\pm 0.9$) × 10¹⁵ protons/cm², ($1.43\pm 0.14$) × 10¹⁶ neutrons/cm², and ($6.5\pm 1.4$) × 10¹⁴ pions/cm², respectively. By observing the charge induced due to the separation of electron–hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be $1.62\pm 0.07\left(\mathrm{stat}\right)\pm 0.16\left(\mathrm{syst}\right)\times$ 10⁻¹⁸ cm²$/(p\mathsf{\mu }\mathrm{m})$, the damage constant for diamond irradiated with fast reactor neutrons to be $2.65\pm 0.13\left(\mathrm{stat}\right)\pm 0.18\left(\mathrm{syst}\right)\times$ 10⁻¹⁸ cm²$/(n\mathsf{\mu }\mathrm{m})$, and the damage constant for diamond irradiated with 200 MeV pions to be $2.0\pm 0.2\left(\mathrm{stat}\right)\pm 0.5\left(\mathrm{syst}\right)\times$ 10⁻¹⁸ cm²$/(\pi \mathsf{\mu }\mathrm{m})$. The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve.