Universal control strategy for anomalous ionic-electronic phenomenology in perovskite solar cells efficiency measurements

Time Transients with Inductive Loop Traces in Metal Halide Perovskites

“…Therefore, it is necessary to transform the immittance spectroscopy data into an admittance response, $$Y\ ( {{\omega}} ) = \tilde{j}( {{\omega}} )/\tilde{V}( {{\omega}} )\ $$. [ 33,60 ] Note that tildes indicate small oscillating voltage and currents. The admittance function, measured in Siemens, can be also represented in terms of the real and imaginary parts, Y (ω) = Y r (ω) + j Y j (ω), where Y r (ω) and Y j (ω) are connected to the conductivity (conductance) and capacitive/inductive (susceptance) contributions.…”

“…Depending on the order of appearance of the capacitive and inductive effects, as indicated in Figure 3, the expressions of the time constants, again the inverse of the characteristic frequencies, will differ with respect to other inductive features (see below). First, the value of the fast time constant, ascribed to the dielectric capacitance, is given by: [ 27,33,59 ] $$$$\begin{equation}{\mathrm{\ \tau }}_{{\mathrm{ST}}} = {\left( {\frac{1}{{{R}_{\mathrm{s}}}} + \frac{1}{{{R}_{\mathrm{b}}}} + \frac{1}{{{R}_{\mathrm{x}}}}} \right)}^{ - 1}\ {C}_{\mathrm{g}}\ \sim \ {R}_{\mathrm{s}}{C}_{\mathrm{g}}\end{equation}$$$$because we consider, for simplicity, that there exists a substantial difference in the value of resistances of the electrical circuit at high bias voltages, and thus series resistance effects can be suppressed and considered negligible in the transient analysis, R s → 0. The resistance “seen” by C g is determined under the assumption that the chemical inductor and the interfacial charging capacitance are discharged (virtual open‐ and short‐circuits, respectively).…”

“…[ 30 ] Impedance measurements are carried out on a particular steady–state determined by a dc voltage bias (no memory). In contrast, time‐domain analysis allows us to handle adequately the past history of the device from the initial conditions and thus, for example, to control the undesired effects of current–voltage hysteresis in photovoltaic applications [ 3,31–33 ] or understand the temporal evolution of the conductance states as a fundamental operation for in‐memory computing. [ 34,35 ] Another fundamental advantage of chronoamperometric experiments, in comparison to the familiar technique of Impedance Spectroscopy, basically includes ultrahigh speed data acquisition to real‐time monitor current evolution during voltage scans, satisfying the time‐invariant assumption of these highly unstable materials and decelerating potential degradation pathways in the devices.…”

Accelerating the Assessment of Hysteresis in Perovskite Solar Cells

“…Theoretically speaking, the necessary time delay for steadystate device operation, Δj(t) → Δj ss , and thus, to eliminate the memory traces (Δj mem (Δt ss ) → 0) that give rise to the current−voltage hysteresis is that for which Δj ss ≫ Δj mem (Δt ss ). 44 We consider the 5% criterion, a typical tolerance band used in control engineering, yielding…”

“…Theoretically speaking, the necessary time delay for steady-state device operation, Δ j ( t ) → Δ j ss , and thus, to eliminate the memory traces (Δ j mem (Δ t ss ) → 0) that give rise to the current–voltage hysteresis is that for which Δ j ss ≫ Δ j mem (Δ t ss ) . We consider the 5% criterion, a typical tolerance band used in control engineering, yielding normalΔ t ss = ( 3 − ln true| g dc g ion − g elect true| ) τ kin In eq appears the classical result 3τ kin described in basic control engineering courses, but also an additional term originated by the ionic–electronic coupling of perovskite solar cells that modulates the conventional suitable time delay and makes emerge the discrepancy between forward and reverse scans when one simply selects the classical value.…”