Photoelectron spectroscopic study on band alignment of poly(3- hexylthiophene-2,5-diyl)/polar-ZnO heterointerface

Takahiro Nagata, Seungjun Oh, Yoshiyuki Yamashita, Hideki Yoshikawa, Norihiro Ikeno, Keisuke Kobayashi, Toyohiro Chikyow, Yutaka Wakayama

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


We used hard X-ray photoelectron spectroscopy (HX-PES) to investigate the polarity effect of ZnO, which has Zn terminated (+ polar) and O terminated (- polar) surfaces, on poly(3-hexylthiophene-2,5-diyl) (P3HT)/ZnO photovoltaic structures. HX-PES, which has a longer inelastic mean free path than conventional X-ray photoelectron spectroscopy, revealed that the open circuit voltage (VOC), estimated from the gap between the highest occupied molecular orbital of P3HT and the conduction band minimum of Zn-polar ZnO, was larger than that of the O-polar ZnO. Although polarity dependence was observed for the electrical structure at the P3HT/ZnO interface, the VOC of the photovoltaic property of Zn-polar ZnO was almost the same as that of O-polar ZnO (~ 0.4 V) due to electron-hole recombination, which degrades the photovoltaic properties at the interface. The HX-PES results also suggested that the recombination could be attributed to the short depletion length of the ZnO surface.

Original languageEnglish
Pages (from-to)194-198
Number of pages5
JournalThin Solid Films
Publication statusPublished - 2014 Mar 3
Externally publishedYes


  • Band alignment
  • Hard X-ray photoelectron spectroscopy
  • Organic/inorganic interface
  • Photovoltaic device
  • Polymer semiconductor
  • Zinc oxide

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry


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