Ionic Accumulation as a Diagnostic Tool in Perovskite Solar Cells: Characterizing Band Alignment with Rapid Voltage Pulses

Nathan S. Hill, Matthew V. Cowley, Nadja Gluck, Miriam H. Fsadni, Will Clarke, Yinghong Hu, Matthew J. Wolf, Noel Healy, Marina Freitag, Thomas J. Penfold, Giles Richardson, Alison B. Walker, Petra J. Cameron, Pablo Docampo

Research output: Contribution to journalArticlepeer-review

4 Citations (SciVal)

Abstract

Despite record-breaking devices, interfaces in perovskite solar cells are still poorly understood, inhibiting further progress. Their mixed ionic-electronic nature results in compositional variations at the interfaces, depending on the history of externally applied biases. This makes it difficult to measure the band energy alignment of charge extraction layers accurately. As a result, the field often resorts to a trial-and-error process to optimize these interfaces. Current approaches are typically carried out in a vacuum and on incomplete cells, hence values may not reflect those found in working devices. To address this, a pulsed measurement technique characterizing the electrostatic potential energy drop across the perovskite layer in a functioning device is developed. This method reconstructs the current-voltage (JV) curve for a range of stabilization biases, holding the ion distribution “static” during subsequent rapid voltage pulses. Two different regimes are observed: at low biases, the reconstructed JV curve is “s-shaped”, whereas, at high biases, typical diode-shaped curves are returned. Using drift-diffusion simulations, it is demonstrated that the intersection of the two regimes reflects the band offsets at the interfaces. This approach effectively allows measurements of interfacial energy level alignment in a complete device under illumination and without the need for expensive vacuum equipment.

Original languageEnglish
Article number2302146
Number of pages12
JournalAdvanced Materials
Early online date5 May 2023
DOIs
Publication statusE-pub ahead of print - 5 May 2023

Bibliographical note

Funding Information:
N.H. and M.V.C. contributed equally to this work. N.H. was supported by the EPSRC‐UKRI DTP and would like to thank Abigail Seddon for help with the interpretation of the dipole moments of benzoic acid groups. M.V.C. was supported by the EPSRC Centre for Doctoral Training in Sustainable Chemical Technologies EP/L016354/1. M.H.F. was supported by the EPSRC Centre for Doctoral Training in Renewable Energy Northeast Universities (ReNU) EP/SO23836/1. M.H.F. thanks Julien Eng for help with visualizing the dipole moments. This research made use of the Rocket High‐Performance Computing service at Newcastle University. P.D. acknowledges funding from the EPSRC under grant agreement EP/T010568/1. N.G. acknowledges funding from the Australian Government through the Australian Centre for Advanced Photovoltaics (ACAP) and the Australian Research Council through the Centre of Excellence in Exciton Science (CE170100026). Y.H. acknowledges funding from the Federal Ministry of Education and Research (BMBF) under project ID 03SF0514A/B. A.B.W. would like to thank the EPSRC for funding from grant EP/SO00763/1 (Supergen Supersolar+ Network+)


Data Availability Statement: The data that support the findings of this study are available from the corresponding author upon reasonable request

Keywords

  • built-in potential
  • interfaces
  • modeling
  • perovskite
  • pulsed measurements

ASJC Scopus subject areas

  • General Materials Science
  • Mechanics of Materials
  • Mechanical Engineering

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