TY - JOUR
T1 - Photoelectron spectroscopic study on band alignment of poly(3- hexylthiophene-2,5-diyl)/polar-ZnO heterointerface
AU - Nagata, Takahiro
AU - Oh, Seungjun
AU - Yamashita, Yoshiyuki
AU - Yoshikawa, Hideki
AU - Ikeno, Norihiro
AU - Kobayashi, Keisuke
AU - Chikyow, Toyohiro
AU - Wakayama, Yutaka
N1 - Funding Information:
We are grateful to HiSOR, Hiroshima University, and JAEA/SPring-8 for the development of HX-PES at BL15XU in SPring-8. The HX-PES measurements were performed under the approval of the NIMS Beamline Station (Proposal No. 2010A 4604 and 2011A 4611). This work was supported in part by the Bilateral Joint Project involving Hungary and Japan established by the Japan Society for the Promotion of Science (JSPS). WPI-MANA was established by World Premier International Research Center Initiative (WPI), the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. We also would like to thank Ms. Mika Watanabe for technical support with the AFM observations.
PY - 2014/3/3
Y1 - 2014/3/3
N2 - 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.
AB - 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.
KW - Band alignment
KW - Hard X-ray photoelectron spectroscopy
KW - Organic/inorganic interface
KW - Photovoltaic device
KW - Polymer semiconductor
KW - Zinc oxide
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U2 - 10.1016/j.tsf.2013.08.018
DO - 10.1016/j.tsf.2013.08.018
M3 - Article
AN - SCOPUS:84893920630
VL - 554
SP - 194
EP - 198
JO - Thin Solid Films
JF - Thin Solid Films
SN - 0040-6090
ER -
