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Open Access Nano Express

Tuning of defects in ZnO nanorod arrays used in bulk heterojunction solar cells

Diana C Iza1, David Muñoz-Rojas1, Quanxi Jia2, Brian Swartzentruber3 and Judith L MacManus-Driscoll1*

Author affiliations

1 Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ, UK

2 MPA CINT, MS K771, Los Alamos National Laboratory, Los Alamos, NM 87545, USA

3 Sandia National Laboratories, MS 1303.1515 Eubank SE, Albuquerque, NM 87123, USA

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Citation and License

Nanoscale Research Letters 2012, 7:655  doi:10.1186/1556-276X-7-655

Published: 27 November 2012

Abstract

With particular focus on bulk heterojunction solar cells incorporating ZnO nanorods, we study how different annealing environments (air or Zn environment) and temperatures impact on the photoluminescence response. Our work gives new insight into the complex defect landscape in ZnO, and it also shows how the different defect types can be manipulated. We have determined the emission wavelengths for the two main defects which make up the visible band, the oxygen vacancy emission wavelength at approximately 530 nm and the zinc vacancy emission wavelength at approximately 630 nm. The precise nature of the defect landscape in the bulk of the nanorods is found to be unimportant to photovoltaic cell performance although the surface structure is more critical. Annealing of the nanorods is optimum at 300°C as this is a sufficiently high temperature to decompose Zn(OH)2 formed at the surface of the nanorods during electrodeposition and sufficiently low to prevent ITO degradation.

Keywords:
ZnO; Solar cells; Bulk heterojunction; Photoluminescence; Defects