Correlation of Spatiotemporal Dynamics of Polarization and Charge Transport in Blended Hybrid Organic–Inorganic Perovskites on Macro- and Nanoscales

Abstract

Progress in flexible organic electronics necessitates a full understanding of how local inhomogeneities impact electronic and ionic conduction pathways and underlie macroscopic device characteristics. We used frequency-and time-resolved macro-and nanoprobe measurements to study spatiotemporal characteristics of multiscale charge transport dynamics in a series of ternary-blended hybrid organic inorganic perovskites (HOIPs) (MA 0.95−x FA x Cs 0.05 PbI 3 ). We show that A-site cation composition defines charge transport mechanisms across broad temporal (10 2 −10 −6 s) and spatial (millimeters−picometers) scales. Ab initio molecular dynamic simulations suggest that insertion of FA results in a dynamic lattice, improved ion transport, and dipole screening. We demonstrate that correlations between macro-and nanoscale measurements provide a pathway for accessing distribution of relaxation in nanoscale polarization and charge transport dynamics of ionically conductive functional perovskites.

Exploring Transport Behavior in Hybrid Perovskites Solar Cells via Machine Learning Analysis of Environmental‐Dependent Impedance Spectroscopy

“…[ 41,68 ] There have been many reports that slow diffusion of ionic defects appears in minutes at room temperature and ambient air. [ 41,47,69,70 ] Ion migration then in turn is in equilibrium within a few minutes when no additional external stimuli such as bias or illumination are applied. Upon filling the chamber with dry N 2 , dramatically decreases from 1.6 × 10 −6 to 0.5 × 10 −6 Ω −1 s ϕ in the first few minutes, and then gradually increases during 24 h to nearly the original value, i.e., 0.7 × 10 −6 Ω −1 s ϕ (see Figure S8 in the Supporting Information).…”

“…The observed time-dependent variation of the charge accumulation at the interface has ionic character as the electronic charge carriers lifetime are likely to be below millisecond time scale. [41,68] There have been many reports that slow diffusion of ionic defects appears in minutes at room temperature and ambient air. [41,47,69,70] Ion migration then in turn is in equilibrium within a few minutes when no additional external stimuli such as bias or illumination are applied.…”

“…To avoid the uncertainties in capacitive components arising from incorrect selection of the circuit model or overfitting, a common mistake, we further analyze impedance spectra by using model-independent distribution of relaxation time (DRT) method, which is commonly used for batteries and electrochemical reactions, and recently applied to HOIPs. [39][40][41] We have recently modified this method by statistical model selection for estimation of the circuit resistances. [39] Due to the availability of open-access databases, machine learning techniques have been rapidly advanced even in the field of perovskites.…”

Ion-driven nanograin formation in early-stage degradation of tri-cation perovskite films

“…These changes resulting from the mixed response of electronic and ionic charge carriers are the focus of a number of studies. 23,25,43 Further analysis and separation of the effects related to charge carriers of different origin are shown in the discussion following Fig. 3-5.…”

“…13,22 Recently, cation migration kinetics were shown to be greatly accelerated by increasing substitution of MA + with FA + ions. 23 In contrast, triple-cation compositions are typically reported to show much lower ion migration activity, which is partially attributed to lower defect concentrations in conjunction with kinetic bar-riers to ion diffusion. 24 Nonetheless, studies still demonstrate large bias-induced organic A-site cation migration on a planar lateral electrode geometry.…”