22-Feb-2023: Talk by Marise García-Batlle

On the 22nd of February, Marise García-Batlle a PhD at the University of Jaume I will give a talk entitled:
High Quality Perovskite Materials for X-Ray Detection: Effect of Mobile Ions on Dark Current Stability
Long-term stability of perovskite-based X ray detectors under working condition remains as the bottle-neck for technological purpose. Several effects are attributed to the presence of mobile ions in these materials such as shielding of the internal electrical field upon biasing and chemical interaction between intrinsic moving defects and electrode materials. As a matter of fact, high and instable dark current levels found in these devices are considered to be connected to ion migration upon polarization. However, it is still unknown how ion displacement alters the electronic current level, and which ionic transport parameters or ionic species determine the time-scale of the current evolution. Therefore, new insights for carrier transport mechanisms, including contact effects in addition to bulk conduction, is still needed due to the complex ionic-electronic nature of this material. In this wok, different compositions of methylammonium lead bromide (MAPbBr3) and methylammonium lead iodine (MAPbI3) perovskites and structures (single- and micro-crystalline) are synthesized and tested by the analysis of the resistance evolution by impedance spectroscopy (IS) measurements and the investigation of current transient responses upon biasing. Our findings corroborate the existence of a coupling between electronic transport and ion kinetics that ultimately establishes the time scale of electronic current. Since ion-originated modulations of electronic properties constitute an essential peace of knowledge to progress into the halide perovskite device physics, this thesis sheds light on the dark current issue by helping to clarify the ongoing debate about potential processes governing detector operation concerning long timescale functioning and current stabilization upon polarization.