Effect of Ion Vacancy Migration on Open‐Circuit Voltage of Perovskite Solar Cells

Abstract

Herein, the influence of ion vacancy migration on the open‐circuit voltage (Voc) of perovskite solar cells (PSCs) by computer simulation is explored. It is found that for PSCs, Voc is determined not only by the carrier recombination process, but also dominantly by the space charge effect of the ion vacancy stored within the Debye layers of the perovskite absorber layer. The migration of ion vacancy affects the ionic charge accumulation within the Debye layers, which affects the screen voltage via the space charge effect and thus determines Vocr and Vocf (open‐circuit voltage for reverse sweep and forward sweep, respectively). By tuning the parameters that determine ion vacancy mobility, the effects of ion vacancy mobility on Vocr and Vocf is investigated.

IonMonger 2.0: software for free, fast and versatile simulation of current, voltage and impedance response of planar perovskite solar cells

“…Simulation results obtained using IonMonger have enabled researchers to tackle a variety of questions relating to the performance and design of PSCs. Examples of such work include: (1) Cave et al [15] demonstrated how to determine activation energies for ion vacancy migration in different perovskite compositions using the information contained in current-voltage (JV) measurements; (2) Courtier [17] used IonMonger to verify a novel theory, termed the ectypal diode theory, for the steady-state performance of a PSC, which is notable for its inclusion of mobile ions; (3) Bennett et al [8] extended this theory to describe the electrochemical impedance response of a PSC and identify a measurable value, analogous to the ideality factor for conventional solar cells, that may be used to diagnose the limiting form of recombination; (4) Riquelme, Castro-Chong, Anta and coworkers [14,54,55] validated this approach by investigating trends in impedance spectra using a combination of IonMonger simulations and investigation of experimental measurements; (5) Diekmann, Le Corre, Stolterfoht and colleagues used IonMonger to study the maximum efficiencies attainable from PSCs incorporating mobile ions in the perovskite layer [23,42], concluding that the presence of mobile ions is detrimental to power conversion efficiency (PCE); (6) Cordoba et al [21] and Lin [45] evaluated another metric, namely the open-circuit voltage. Lin also simulated the impact of mobile ions on the short-circuit current [46].…”

Influence of Ion Vacancy Migration on Short‐Circuit Current of Perovskite Solar Cells

“…The ion vacancy mobility μ I = ( q / k B T ) D inf exp(– E a / k B T ) is determined by the parameters of ion activation energy E a , high‐temperature ion diffusion coefficient D inf , and ambient temperature T . [ 20,23–27 ] By controlling these parameters, the effect of parameter μ I on J sc is explored. Our work is achieved by implementing the IonMonger simulator presented by Courtier et al [ 19 ]…”

“…According to the simulated migration process of ion vacancy during the whole J-V scans, we explore how the ion vacancy migration affects these component currents. The ion vacancy mobility μ I ¼ (q/k B T ) D inf exp(-E a /k B T ) is determined by the parameters of ion activation energy E a , high-temperature ion diffusion coefficient D inf , and ambient temperature T. [20,[23][24][25][26][27] By controlling these parameters, the effect of parameter μ I on J sc is explored. Our work is achieved by implementing the IonMonger simulator presented by Courtier et al [19] 2.…”

“…However, the short‐circuit current ( J sc ), open‐circuit voltage ( V oc ), PCE, and FF all affect the cells’ whole performance. Lin [ 20 ] found some interesting characteristics of V oc and presented a theory to describe it. Based on experimental measurement and simulation, respectively, Jarla et al [ 21 ] and Cave et al [ 6 ] found that by enlarging the scan rate region of applied voltage, the ion migration will show an obvious effect on J sc .…”

Saturation of Hysteretic Effect in Current–Voltage Characteristics of Perovskite Solar Cells

“…As a result, a negligible hysteretic effect is observed. Further, Lin [17,18] extended the work to observe the role of the rate of voltage sweep on the solar cell performance parameters such as open-circuit voltage and short-circuit current. He showed that by tuning the rate of voltage sweep between 10 À5 and 10 5 Vs À1 , the mobility of the ionic vacancy gets modified which, in turn, directly affects the value of open-circuit voltage and short-circuit current.…”