Hysteresis, Impedance, and Transients Effects in Halide Perovskite Solar Cells and Memory Devices Analysis by Neuron‐Style Models

Abstract

Halide perovskites are at the forefront of active research in many applications, such as high performance solar cells, photodetectors, and synapses and neurons for neuromorphic computation. As a result of ion transport and ionic‐electronic interactions, current and recombination are influenced by delay and memory effects that cause hysteresis of current–voltage curves and long switching times. A methodology to formulate device models is shown, in which the conduction and recombination electronic variables are influenced by internal state variables. The models are inspired in biological frameworks of the Hodgkin–Huxley class of models. Here, the theoretical precedents, the main physical components of the models, and their application to describe dynamical measurements in halide perovskite devices are summarized. The application of several measurement methods is analyzed, as the current–voltage curves at different scan rates, the impedance spectroscopy response, and the time transients. The transition from normal (capacitive) to inverted (inductive) hysteresis, and the convergence of current–voltage curves to a stable value, are described. It is proposed that neuron‐style models capture dynamical complexity with a favorable economy of parameters, toward the identification of the dominant global dynamic processes across a wide voltage span that determines the practical response of different types of devices.

Capacitive and Inductive Characteristics of Volatile Perovskite Resistive Switching Devices with Analog Memory

“…Notably, these capacitive and inductive characteristics in the I – V curves of memristor devices have been correlated with the observed impedance spectroscopy measurements, , and transient current responses. , This indicates that the nonlinear dynamics of the resistive switching is more appropriately related as a change in the overall device impedance . This complex nonlinear interplay among the resistive, capacitive, and inductive effects is manifested as a frequency-dependent impedance modulation resulting in distinct resistive switching specific to the device configuration …”

“…Increasing the upper vertex up to 0.75 V ( Figure 3 b), the I – V response exhibits a pinched hysteresis with a crossing point at ∼0.38 V. This crossing point varies depending on the scan rate of the I – V measurement, as well as the device operational stability ( Figure S1 ), indicating a dynamic response of the state transitions from capacitive to inductive regimes. 26 , 43 Notably, the device consistently exhibits a normal hysteresis for voltages below the crossing point, which transitions to an inverted hysteresis for voltages above the crossing point. This inverted hysteresis loop in the I – V response is attributed to an inductive time domain response where the forward scan has lower current levels than the reverse scan, typically observed in MAPbBr 3 -based solar cells.…”

“…In the linear scale with an upper vertex of 0.25 V (Figure a), the characteristic I – V response exhibits high current levels in the forward scan direction and low current levels in the reverse scan direction, commonly referred as normal hysteresis, attributed to a fully capacitive response. ,, The corresponding characteristic I – V response in the semilogarithmic scale is shown in Figure d, indicating the voltage range in the fully capacitive regime. Increasing the upper vertex up to 0.75 V (Figure b), the I – V response exhibits a pinched hysteresis with a crossing point at ∼0.38 V. This crossing point varies depending on the scan rate of the I – V measurement, as well as the device operational stability (Figure S1), indicating a dynamic response of the state transitions from capacitive to inductive regimes. , Notably, the device consistently exhibits a normal hysteresis for voltages below the crossing point, which transitions to an inverted hysteresis for voltages above the crossing point. This inverted hysteresis loop in the I – V response is attributed to an inductive time domain response where the forward scan has lower current levels than the reverse scan, typically observed in MAPbBr 3 -based solar cells. ,, The corresponding response in the semilogarithmic scale is shown in Figure e, indicating the transition from a fully capacitive to an inductive regime.…”

“…25 This complex nonlinear interplay among the resistive, capacitive, and inductive effects is manifested as a frequency-dependent impedance modulation resulting in distinct resistive switching specific to the device configuration. 26 From classical circuit theory, the current through an ideal capacitor with a capacitance C is given by I = C dV/dt, while the voltage through an ideal inductor with an inductance L is given by V = L dI/dt. Upon the application of a periodic voltage input, the I−V curves (Figure 1a) of the capacitor and the inductor exhibit normal hysteresis (higher current levels in the forward scan than in the reverse scan) and inverse hysteresis (higher current levels in the reverse scan than in the forward scan), respectively.…”

“… 25 This complex nonlinear interplay among the resistive, capacitive, and inductive effects is manifested as a frequency-dependent impedance modulation resulting in distinct resistive switching specific to the device configuration. 26 …”