Dual wavelength (ultraviolet and green) photodetectors using solution processed Zinc Oxide nanoparticles

Mohammed Ibrahem, Emanuele Verrelli, Khue Lai, Georgios Kyriakou, Adam Lee, Mark Isaacs, Fei Cheng, Mary O'Neill

Research output: Contribution to journalArticlepeer-review


Narrow-band photoconductivity with a spectral width of 0.16 eV is obtained from solution-processed colloidal ZnO nanocrystals beneath the band-edge at 2.25 eV. A new model involving electron transfer from deep defects to discrete shallow donors is introduced to explain the narrow spectrum and the exponential form of the current rise and decay transients. The defects are tentatively assigned to neutral oxygen vacancies. The photocurrent responsivity can be enhanced by storage in air and this correlates with the formation of carbonate surface species by capture of carbon dioxide during storage. This controllability is exploited to develop a low-cost and scalable photolithographic approach to pixelate photodetectors for applications such as object discrimination, sensing etc. The spectral response can be spatially patterned so that dual (ultraviolet and green) and single (ultraviolet only) wavelength detecting ZnO pixels can be produced on the same substrate. This presents a new sensor mode with applications in security or full colour imaging.
Original languageEnglish
Pages (from-to)36971–36979
JournalACS Applied Materials and Interfaces
Issue number42
Early online date26 Sept 2017
Publication statusPublished - 25 Oct 2017

Bibliographical note

Copyright © 2017 American Chemical Society.
This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials and Interfaces, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acsami.7b08092.

Funding: Iraqi Ministry of Higher Education and Scientific Research, EPSRC grant EP/J001597/1.


  • persistent photoconductivity
  • ZnO nanoparticles
  • photolithography
  • imaging photodetectors
  • defects


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