Engineering Stress in Perovskite Solar Cells to Improve Stability

Nicholas Rolston, Kevin A. Bush, Adam D. Printz, Aryeh Gold-Parker, Yichuan Ding, Michael F. Toney, Michael D. McGehee, Reinhold H. Dauskardt

Research output: Contribution to journalArticlepeer-review

129 Scopus citations

Abstract

An overlooked factor affecting stability: the residual stresses in perovskite films, which are tensile and can exceed 50 MPa in magnitude, a value high enough to deform copper, is reported. These stresses provide a significant driving force for fracture. Films are shown to be more unstable under tensile stress—and conversely more stable under compressive stress—when exposed to heat or humidity. Increasing the formation temperature of perovskite films directly correlates with larger residual stresses, a result of the high thermal expansion coefficient of perovskites. Specifically, this tensile stress forms upon cooling to room temperature, as the substrate constrains the perovskite from shrinking. No evidence of stress relaxation is observed, with the purely elastic film stress attributed to the thermal expansion mismatch between the perovskite and substrate. Additionally, the authors demonstrate that using a bath conversion method to form the perovskite film at room temperature leads to low stress values that are unaffected by further annealing, indicating complete perovskite formation prior to annealing. It is concluded that reducing the film stress is a novel method for improving perovskite stability, which can be accomplished by lower formation temperatures, flexible substrates with high thermal expansion coefficients, and externally applied compressive stress after fabrication.

Original languageEnglish (US)
Article number1802139
JournalAdvanced Energy Materials
Volume8
Issue number29
DOIs
StatePublished - Oct 15 2018
Externally publishedYes

Keywords

  • degradation
  • flexible
  • reliability
  • strain
  • thermal expansion

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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