Assessing the Drawbacks and Benefits of Ion Migration in Lead Halide Perovskites

Abstract

Since the inception of the unprecedented rise of halide perovskites for photovoltaic research, ion migration has shadowed this material class with undesirable hysteresis and degradation effects, limiting its practical implementations. Unfortunately, the localized doping and electrochemical reactions triggered by ion migration cause many more undesirable effects that are often unreported or misinterpreted because they deviate from classical semiconductor behavior. In this Perspective, we provide a concise overview of such effects in halide perovskites, such as operational instability in photovoltaics, polarization-induced abnormal external quantum efficiency in light-emitting diodes, and energy channel shift and anomalous sensitivities in hard radiation detection. Finally, we highlight a unique use case of exploiting ion migration as a boon to design emerging memory technologies such as memristors for information storage and computing.

Ionic-electronic halide perovskite memdiodes enabling neuromorphic computing with a second-order complexity

“…In ABX 3 halide perovskites [A = CH 3 NH 3 , CH(NH 2 ) 2 , Cs, Rb; B = Pb, Sn, Ge; X = I, Br, Cl, F], the soft lattice allows easy diffusion of ions across the octahedral structure, resulting in intimate coupling of ionic transport with electronic transport (of electrons and holes). Ionic transport is the process of hopping between ions' equilibrium locations in interstitials, defects, or defect hopping (29). Hence, halide perovskite is an archetypal mixed ionic-electronic conductor (30).…”

Mechanistic and Kinetic Analysis of Perovskite Memristors with Buffer Layers: The Case of a Two-Step Set Process

“…Incorporation of a large cation dopant, such as ethylenediammonium (en), has been proven to substatially improve the device stability to record endurances of 1.2 × 10 4 cycles. 30 To investigate the effect of the buffer layer on the switching properties, the performance of memristors containing either PCBM or PMMA as the buffer layer is compared with that of devices that contain no buffer layer. PCBM and PMMA are materials very different from the point of view of their Table 1.…”

“…Metal halide perovskite materials are versatile candidates for memory applications as they benefit from mixed ionic–electronic conduction due to ionic halide defect displacement resulting in intrinsic memory effects. − Metal halide perovskites have a chemical structure of ABX 3 , where A is a monovalent cation (i.e., MA = CH 3 NH 3 + ), B is a divalent cation (i.e., Pb 2+ ), and X is a halide anion (i.e., I – ). With the flexibility of the perovskite structure as the material platform, it possesses a broad range of switching physics suitable for a wide variety of neuromorphic computing achitectures . Perovskite-based memristive devices have been demonstrated to function as artificial synapses exhibiting essential synaptic behaviors for neuromuscular systems, pupil reflex, and light-sensitive optogenetic applications. − Additionally, integration of two-dimensional structures, , mixed formulations, , and nanocrystals , further increases the already vast degrees of freedom or state variables in perovskite-based memristors allowing tunability and versatility specific to the desired implementation.…”

“…It is worth noting that the memristor device configuration is designed to emphasize the kinetics and dynamics of the resistive switching mechanism. Incorporation of a large cation dopant, such as ethylenediammonium (en), has been proven to substatially improve the device stability to record endurances of 1.2 × 10 4 cycles …”

“…With the flexibility of the perovskite structure as the material platform, it possesses a broad range of switching physics suitable for a wide variety of neuromorphic computing achitectures. 30 Perovskite-based memristive devices have been demonstrated to function as artificial synapses exhibiting essential synaptic behaviors for neuromuscular systems, pupil reflex, and light-sensitive optogenetic applications. 31 − 34 Additionally, integration of two-dimensional structures, 35 , 36 mixed formulations, 37 , 38 and nanocrystals 21 , 39 further increases the already vast degrees of freedom or state variables in perovskite-based memristors allowing tunability and versatility specific to the desired implementation.…”