Unraveling the Key Relationship Between Perovskite Capacitive Memory, Long Timescale Cooperative Relaxation Phenomena, and Anomalous J–V Hysteresis

Abstract

Capacitive response at long time scales seems to remain an elusive feature in the analysis of the electrical properties of perovskite‐based solar cells. It belongs to one of the critical anomalous effects that arises from the characteristic phenomenology of this type of emerging photovoltaic devices. Thereby, accurately deducing key capacitance feature of new light harvesting perovskites from electrical measurements represents a significant challenge regarding the interpretation of physical processes and the control of undesired mechanisms, such as slow dynamic effects and/or current density–voltage (J–V) hysteresis. Herein, it is shown that long timescale mechanisms that give rise to hysteresis in stable and high‐efficiency quadruple‐cation perovskites are not due to a classical capacitive behavior in the sense of ideal charge accumulation processes. Instead, it is a phenomenological consequence of slow memory‐based capacitive currents and the underlying cooperative relaxations. A fractional dynamics approach, based on the idea of capacitance distribution in perovskite devices, reliably models the slow transient phenomena and the consequent scan‐rate‐ and bias‐dependent hysteresis. Observable for a wide variety of photovoltaic halide perovskites, distributed capacitive effects are rather universal anomalous phenomena, which can be related to the long‐time electrical response and hysteresis.

RETRACTED: Improving the Structural, Optical and Photovoltaic Properties of Sb- and Bi- Co-Doped MAPbBr3 Perovskite Solar Cell

“…It is critical to choose the right electrical structure for inorganic semiconductor materials in hybrid solar cells if you want to improve performance [3]. Enrique Hernández-Balaguera et al [4,5] established a connection between perovskite memory effects, anomalous evolution or non-predictable response of the transient, structural complexity of PSCs, CPE features in IS, fractional dynamics, J-V hysteresis and Cole-Cole dielectric mode. In the few years since their discovery, MAPb halide PSCs have become more efficient and advanced more rapidly than any other solar cell.…”

Non-Debye Relaxations: The Ups and Downs of the Stretched Exponential vs. Mittag–Leffler’s Matchings

“…IIa) for α = 1/3 and τ = 1. The characteristic exponents Ψ KWW (s) and Φ KWW (s) have been calculated using Equation ( 8) whereas Ψ CC (s) and Φ CC (s) are given by Equation (14). The latter ones are, respectively, multiplied and divided by [Γ(4/3)] −1 .…”

“…Much more recently it has appeared in quantum mechanics [7] where it describes the so-called Maxwell's fish eye problem. An interesting application, coming from the interface of the basic and applied science, is using the CC pattern in electrochemistry [8,9], bioelectrochemistry [10][11][12][13] and photovoltaics [14]. Effects of distributed, i.e., non-Debye, relaxation processes, inhomogeneities of the system and possible deviations from the Gaussian diffusion spreading lead to non-ideal interfacial behavior.…”

“…Such an approach has been presented in investigations [10][11][12][13] where it has been also noticed that asymptotic properties of the (standard) Mittag-Leffler function for short times agree with those of the KWW function and that the Mittag-Leffler function interpolates between the KWW for short times and the power-like behavior for long times. Among consequences of this property it has been found that the (standard) Mittag-Leffler function appears useful not only in studies of short time effects characteristic for biochemical processes [11,13] but also in analysis of the long time phenomena occurring in the perovskite solar cells [12,14]. Here we want to address the readers' attention and emphasize that attempts to fit the data by the (standard) Mittag-Leffler function instead of the KWW decay suggest to try the use of other function belonging to the Mittag-Leffler family, especially if one would be interested in search of matchings functioning beyond the leading order of small t asymptotics.…”

Fundamentals of Hysteresis in Perovskite Solar Cells: From Structure‐Property Relationship to Neoteric Breakthroughs

“…This fractional dynamic approach is based on the capacitance distribution phenomenon, and it depends on the slow transient phenomena that result in scan rate and bias-dependent hysteresis. [93] The capacitive hysteresis originates from the accommodation of both ionic and electronic charges at the interfaces between the perovskite layer and electrodes (ETL & HTL). This accommodation of charges produced an electric field in such a direction to repeal the incoming electron.…”