Cobalt Oxide (CoOx) as an Efficient Hole-Extracting Layer for High-Performance Inverted Planar Perovskite Solar Cells

Ahmed Esmail Shalan, Tomoya Oshikiri, Sudhakar Narra, Mahmoud M. Elshanawany, Kosei Ueno, Hui Ping Wu, Keisuke Nakamura, Xu Shi, Eric Wei Guang Diau, Hiroaki Misawa

Research output: Contribution to journalArticlepeer-review

104 Citations (Scopus)


CoOx is a promising hole-extracting layer (HEL) for inverted planar perovskite solar cells with device configuration ITO/CoOx/CH3NH3PbI3/PCBM/Ag. The devices fabricated according to a simple solution procedure showed the best photovoltaic performance attaining power conversion efficiency (PCE) of 14.5% under AM 1.5 G 1 sun irradiation, which is significantly superior to those of materials fabricated with a traditional HEL such as PEDOT:PSS (12.2%), NiOx (10.2%), and CuOx (9.4%) under the same experimental conditions. We characterized the chemical compositions with XPS, crystal structures with XRD, and film morphology with SEM/AFM techniques. Photoluminescence (PL) spectra and the corresponding PL decays for perovskite deposited on varied HEL films were recorded to obtain the hole-extracting characteristics, for which the hole-extracting times show the order CoOx (2.8 ns) < PEDOT:PSS (17.5 ns) < NiOx (22.8 ns) < CuOx (208.5 ns), consistent with the trend of their photovoltaic performances. The reproducibility and enduring stability of those devices were examined to show the outstanding long-term stability of the devices made of metal oxide HEL, for which the CoOx device retained PCE ≈ 12% for over 1000 h.

Original languageEnglish
Pages (from-to)33592-33600
Number of pages9
JournalACS Applied Materials and Interfaces
Issue number49
Publication statusPublished - 2016 Dec 14
Externally publishedYes


  • cobalt oxide
  • hole-extraction layer
  • perovskite solar cell
  • photoluminescence
  • photovoltaic devices

ASJC Scopus subject areas

  • Materials Science(all)


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