Origin of Extended UV Stability of 2D Atomic Layer Titania-Based Perovskite Solar Cells Unveiled by Ultrafast Spectroscopy

Anusha Puliparambil Thilakan, Jia Xing Li, Tzu Pei Chen, Shao Sian Li*, Chun Wei Chen, Minoru Osada, Kazuhito Tsukagoshi, Takayoshi Sasaki, Atsushi Yabushita, Kaung-Hsiung Wu, Chih-Wei Luo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The inherent instability of UV-induced degradation in TiO2-based perovskite solar cells was largely improved by replacing the anatase-phase compact TiO2 layer with an atomic sheet transport layer (ASTL) of two-dimensional (2D) Ti1-δO2. The vital role of microscopic carrier dynamics that govern the UV stability of perovskite solar cells was comprehensively examined in this work by performing time-resolved pump-probe spectroscopy. In conventional perovskite solar cells, the presence of a UV-active oxygen vacancy in compact TiO2 prohibits current generation by heavily trapping electrons after UV degradation. Conversely, the dominant vacancy type in the 2D Ti1-δO2 ASTL is a titanium vacancy, which is a shallow acceptor and is not UV-sensitive. Therefore, it significantly suppresses carrier recombination and extends UV stability in perovskite solar cells with a 2D Ti1-δO2 ASTL. Other carrier dynamics, such as electron diffusion, electron injection, and hot hole transfer processes, were found to be less affected by UV irradiation. Quantitative pump-probe data clearly show a correlation between the carrier dynamics and UV aging of perovskite solar cells, thus providing a profound insight into the factors driving UV-induced degradation in perovskite solar cells and the origin of its performance.

Original languageEnglish
Pages (from-to)21473-21480
Number of pages8
JournalACS Applied Materials and Interfaces
Issue number24
StatePublished - 19 Jun 2019


  • UV degradation
  • electron transport layer
  • perovskite solar cell
  • pump-probe technique
  • two-dimensional metal oxide
  • ultrafast mechanism


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