n-Type Transition Metal Oxide as a Hole Extraction Layer in PbS Quantum Dot Solar Cells

Jianbo Gao, Craig L. Perkins, Joseph M. Luther, Mark C. Hanna, Hsiang Yu Chen, Octavi E. Semonin, Arthur J. Nozik, Randy J. Ellingson, Matthew C. Beard

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249 Scopus Citations


The n-type transition metal oxides (TMO) consisting of molybdenum oxide (MoOx) and vanadium oxide (V2Ox) are used as an efficient hole extraction layer (HEL) in heterojunction ZnO/PbS quantum dot solar cells (QDSC). A 4.4% NREL-certified device based on the MoOx HEL is reported with Al as the back contact material, representing a more than 65% efficiency improvement compared with the case of Au contacting the PbS quantum dot (QD) layer directly. We find the acting mechanism of the hole extraction layer to be a dipole formed at the MoOx and PbS interface enhancing band bending to allow efficient hole extraction from the valence band of the PbS layer by MoOx. The carrier transport to the metal anode is likely enhanced through shallow gap states in the MoOx layer.

Original languageAmerican English
Pages (from-to)3263-3266
Number of pages4
JournalNano Letters
Issue number8
StatePublished - 2011

NREL Publication Number

  • NREL/JA-5900-52074


  • band bending
  • gap states
  • hole extraction layer
  • quantum dot
  • solar cell
  • Transition metal oxide


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