The optoelectronic properties of halide perovskite materials have fostered their utilization in many applications. Unravelling their working mechanisms remains challenging because of their mixed ionic–electronic conductive nature. By registering, with high reproducibility, the long-time current transients of a set of single-crystal methylammonium lead tribromide samples, the ion migration process was proved. Sample biasing experiments (ionic drift), with characteristic times exhibiting voltage dependence as ∝ V^–3/2, is interpreted with an ionic migration model obeying a ballistic-like voltage-dependent mobility (BVM) regime of space-charge-limited current. Ionic kinetics effectively modify the long-time electronic current, while the steady-state electronic currents’ behavior is nearly ohmic. Using the ionic dynamic doping model (IDD) for the recovering current at zero bias (ion diffusion), the ionic mobility is estimated to be ∼10^–6 cm² V^–1 s^–1. Our findings suggest that ionic currents are negligible in comparison to the electronic currents; however, they influence them via changes in the charge density profile.

Metal halide perovskites (MHPs) are disruptive materials for a vast class of optoelectronic devices. The presence of electronic trap states has been a tough challenge in terms of characterization and thus mitigation. Many attempts based on electronic spectroscopies have been tested, but due to the mixed electronic-ionic nature of MHP conductivity, many experimental results retain a large ambiguity in resolving electronic and ionic charge contributions. Here we adapt a method, previously used in highly resistive inorganic semiconductors, called photoinduced current transient spectroscopy (PICTS) on lead bromide 2D-like ((PEA)₂PbBr₄) and standard "3D" (MAPbBr₃) MHP single crystals. We present two conceptually different outcomes of the PICTS measurements, distinguishing the different electronic and ionic contributions to the photocurrents based on the different ion drift of the two materials. Our experiments unveil deep level trap states on the 2D, "ion-frozen" (PEA)₂PbBr₄ and set new boundaries for the applicability of PICTS on 3D MHPs.

Research on metal halide perovskites as absorbers for X-ray detection is an attractive subject due to the optimal optoelectronic properties of these materials for high-sensitivity applications. However, the contact degradation and the long-term instability of the current limit the performance of the devices, in close causality with the dual electronic-ionic conductivity of these perovskites. Herein, millimeter-thick methylammonium-lead bromide (MAPbBr₃) single and polycrystalline samples are approached by characterizing their long-term dark current and photocurrent under X-ray incidence. It is shown how both the dark current and the sensitivity of the detectors follow similar trends at short-circuit (V = 0 V) after biasing. By performing drift-diffusion numerical simulations, it is revealed how large ionic-related built-in fields not only produce relaxations to equilibrium lasting up to tens of hours but also continue to affect the charge kinetics under homogeneous low photogeneration rates. Furthermore, a method is suggested for estimating the ionic mobility and concentration by analyzing the initial current at short-circuit and the characteristic diffusion times.

The inherent ion migration in metal halide perovskite materials is known to induce deleterious and highly unstable dark currents in X‐ and γ‐ray detectors based on those compounds upon bias application. Dark current slow drift with time is identified as one of the major drawbacks for these devices to satisfy industrial requirements. Because dark current establishes the detectability limit, current evolution, and eventual growth may mask photocurrent signals produced by incoming X‐ray photons. Relevant information for detector assessment is ion‐related parameters such as ion concentration, ion mobility, and ionic space‐charge zones that are eventually built near the outer contacts upon detector biasing. A combined experimental (simple measurement of dark current transients) and 1D numerical simulation method is followed here using single‐crystal and microcrystalline millimeter‐thick methylammonium‐lead bromide that allows extracting ion mobility within the range of µ_ion ≈ 10⁻⁷ cm² V⁻¹ s⁻¹, while ion concentration values approximate N_ion ≈ 10¹⁵ cm⁻³, depending on the perovskite crystallinity.