Examinando por Autor "Bisquert, Juan"

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Accelerating the Assessment of Hysteresis in Perovskite Solar Cells
(American Chemical Society, 2024-01-17) Balaguera, Enrique H.; Bisquert, Juan
Halide perovskite materials have reached important milestones in the photovoltaic field, positioning them as realistic alternatives to conventional solar cells. However, unavoidable kinetic phenomena have represented a major concern for reliable steady-state performance assessment from standard current–voltage measurements. In particular, the dynamic hysteresis of current–voltage curves requires relatively long stabilization to achieve a credible figure for the power conversion efficiency. Hysteresis is caused by complex current transient phenomena that become active during staircase voltammetry. Here, we address the root of this problem. We pinpoint the dynamic characteristics behind the slow transient responses to strategically predict a minimum time delay and thus estimate the power conversion efficiency under steady-state conditions. Circuit-element analysis and impedance spectroscopy confirm our predictions based on an advanced transient study. Our results fundamentally explore the possibility of reducing data time acquisition in a reliable performance assessment, providing disruptive solutions and perspectives toward systematic production of photovoltaic perovskites.
Negative Transient Spikes in Halide Perovskites
(ACS, 2022) Hernández-Balaguera, Enrique; Bisquert, Juan
The internal crossfire of ionic and electronic effects in perovskite devices forms a complex analysis problem that has not been fully solved yet. Specifically, halide photovoltaic perovskites show a photoinduced ionic inductance behavior in current transient measurements, evidenced by ubiquitous negative spikes. Here, we provide a consolidated interpretation of these observed chemical mechanisms by independent measurement routes (frequency and time domain) in order to solve an elusive topic in the development of perovskite solar cells for more than a decade. From this operational pathway, we specifically study the light-dependent negative overshoot photocurrent phenomena in the time-domain discharge of the chemical inductor, which is a transversal mechanism found in a multitude of chemical, biological, and material systems. Our results establish a general framework to understand the inductive transient effects observable in new and important applications of halide perovskites, capable of emulating the electrical activity of neurons and synapses when acting as memristors.
Physical model for the current-voltage hysteresis and impedance of halide perovskite memristors
(ACS, 2022-03-11) Berruet, Mariana; Pérez-Martínez, Jose Carlos; Romero, Beatriz; Gonzales, Cedric; Añ-Mayouf, Abdullah; Guerrero, Antonio; Bisquert, Juan
An investigation of the kinetic behavior of MAPbI(3) memristors shows that the onset voltage to a high conducting state depends strongly on the voltage sweep rate, and the impedance spectra generate complex capacitive and inductive patterns. We develop a dynamic model to describe these features and obtain physical insight into the coupling of ionic and electronic properties that produce the resistive switching behavior. The model separates the memristive response into distinct diffusion and transition-state-formation steps that describe well the experimental current-voltage curves at different scan rates and impedance spectra. The ac impedance analysis shows that the halide perovskite memristor response contains the composition of two inductive processes that provide a huge negative capacitance associated with inverted hysteresis. The results provide a new approach to understand some typical characteristics of halide perovskite devices, such as the inductive behavior and hysteresis effects, according to the time scales of internal processes.
Time Transients with Inductive Loop Traces in Metal Halide Perovskites
(Wiley, 2023) Hernández-Balaguera, Enrique; Bisquert, Juan
Metal halide perovskites are archetypal ionic-electronic materials with great prospects for optoelectronic applications. Among the rich variety of physics exhibited by ionic-electronic conduction, here, those most relevant to optoelectronic devices in which ionic mechanisms introduce a kinetic delay in the electronic phenomena are analyzed. The attention is focused on the inductive loop features and a dynamical model is developed to describe the corresponding complex multiscale dynamics in the time domain under experimental conditions, finally explaining the fundamental structure of the current transient responses in halide perovskite semiconductors. Based on complex capacitive and inductive patterns extensively studied in impedance measurements, an adequate interpretation of time domain methods capable of monitoring charge-carrier dynamics is produced. Therefore, this methodology identifies the characteristic parameters of all types of transient dynamics in metal halide perovskites, providing a suitable connection of correlated techniques, including impedance and chronoamperometric experiments, toward a robust interpretation of the device response. The scope of the method is fairly general, since these counterintuitive transient effects are observable not only in metal halide perovskites, but also in multiple materials and processes, mainly in different research fields pertaining to electrochemistry and electronics.