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Ionic Field Screening in MAPbBr3 Crystals Revealed from Remnant Sensitivity in X-ray Detection
Agustin O Alvarez1, Ferdinand Lédée2, Marisé García-Batlle1
1Institute of Advanced Materials, Universitat Jaume I, 12071 Castelló, Spain.
ACS Physical Chemistry Au
|July 31, 2023
Summary
Metal halide perovskites show promise for X-ray detection, but instability is an issue. This study reveals how ion migration affects device performance and suggests a method to quantify ionic properties for improved stability.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Detector Physics
Background:
- Metal halide perovskites offer optimal optoelectronic properties for high-sensitivity X-ray detection.
- Device performance is limited by contact degradation and current instability, linked to dual electronic-ionic conductivity.
- Methylammonium-lead bromide (MAPbBr3) is a key material for these applications.
Purpose of the Study:
- To characterize the long-term dark current and photocurrent of MAPBBr3 detectors under X-ray incidence.
- To investigate the influence of ionic conductivity on device stability and performance.
- To develop a method for estimating ionic mobility and concentration in perovskite X-ray detectors.
Main Methods:
- Experimental characterization of millimeter-thick MAPBBr3 single and polycrystalline samples.
- Measurement of dark current and photocurrent under X-ray irradiation at short-circuit after biasing.
- Drift-diffusion numerical simulations to model charge kinetics and ionic field effects.
Main Results:
- Dark current and detector sensitivity exhibit similar trends at short-circuit after applied bias.
- Ionic-related built-in fields significantly impact charge kinetics, causing long relaxation times (up to tens of hours).
- Ionic fields continue to affect charge kinetics even under low photogeneration rates.
Conclusions:
- Dual electronic-ionic conductivity in perovskites leads to performance limitations due to ion migration.
- Understanding and mitigating the effects of ionic fields are crucial for stable and sensitive X-ray detectors.
- A novel method for estimating ionic mobility and concentration is proposed, aiding in material optimization.
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