Understanding the Effect of Lead Iodide Excess on the Performance of Methylammonium Lead Iodide Perovskite Solar Cells

Zeeshan Ahmad, Rebecca Scheidt, Matthew Hautzinger, Kai Zhu, Matthew Beard, Giulia Galli

Research output: Contribution to journalArticlepeer-review

19 Scopus Citations

Abstract

The presence of unreacted lead iodide in organic-inorganic lead halide perovskite solar cells is widely correlated with an increase in power conversion efficiency. We investigate the mechanism for this increase by identifying the role of surfaces and interfaces present between methylammonium lead iodide perovskite films and excess lead iodide. We show how type I and II band alignments arising under different conditions result in either passivation of surface defects or hole injection. Through first-principles simulations of solid-solid interfaces, we find that lead iodide captures holes from methylammonium lead iodide and modulates the formation of defects in the perovskite, affecting recombination. Using surface-sensitive optical spectroscopy techniques, such as transient reflectance and time-resolved photoluminescence, we show how excess lead iodide affects the diffusion and surface recombination velocity of charge carriers in methylammonium lead iodide films. Our coupled experimental and theoretical results elucidate the role of excess lead iodide in perovskite solar cells.

Original languageAmerican English
Pages (from-to)1912-1919
Number of pages8
JournalACS Energy Letters
Volume7
Issue number6
DOIs
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.

NREL Publication Number

  • NREL/JA-5900-82034

Keywords

  • metal halide perovskite
  • transient spectroscopy

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