Enhanced efficiency in plastic solar cells via energy matched solution processed NiO x interlayers

K. Xerxes Steirer, Paul F. Ndione, N. Edwin Widjonarko, Matthew T. Lloyd, Jens Meyer, Erin L. Ratcliff, Antoine Kahn, Neal R. Armstrong, Calvin J. Curtis, David S. Ginley, Joseph J. Berry, Dana C. Olson

Research output: Contribution to journalArticlepeer-review

309 Scopus citations


We show enhanced efficiency and stability of a high performance organic solar cell (OPV) when the work-function of the hole collecting indium-tin oxide (ITO) contact, modifi ed with a solution-processed nickel oxide (NiO x) hole-transport layer (HTL), is matched to the ionization potential of the donor material in a bulk-heterojunction solar cell. Addition of the NiO x HTL to the hole collecting contact results in a power conversion Efficiency ( PCE ) of 6.7%, which is a 17.3% net increase in performance over the 5.7% PCE achieved with a poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) HTL on ITO. The impact of these NiO x films is evaluated through optical and electronic measurements as well as device modeling. The valence and conduction band energies for the NiO x HTL are characterized in detail through photoelectron spectroscopy studies while spectroscopic ellipsometry is used to characterize the optical properties. Oxygen plasma treatment of the NiO x HTL is shown to provide superior contact properties by increasing the ITO/NiO x contact work-function by 500 meV. Enhancement of device performance is attributed to reduction of the band edge energy offset at the ITO/NiO x interface with the poly(N-9′-heptadecanyl-2,7-carbazole-alt- 5,5-(4′,7′-di- 2-thienyl-2′,1′,3′-benzothidiazole) (PCDTBT):[6,6]-phenyl-C61 butyric acid methyl ester PCBM and [6,6]-phenyl-C71 butyric acid methyl ester (PC 70 BM) active layer. A high work-function hole collecting contact is therefore the appropriate choice for high ionization potential donor materials in order to maximize OPV performance.

Original languageEnglish (US)
Pages (from-to)813-820
Number of pages8
JournalAdvanced Energy Materials
Issue number5
StatePublished - Oct 2011

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • General Materials Science


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