Nanoscale structure-property relationships in low-temperature solution-processed electron transport layers for organic photovoltaics

Jiaqi Zhang, Maurizio Morbidoni, Claire H. Burgess, Jiaying Wu, Tian Du, Khallil Harrabi, David J. Payne, James R. Durrant, Martyn A. McLachlan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Here we elucidate the nanostructure-property relationships in low-temperature, solution-processed ZnO based thin films employed as novel electron transport layers (ETLs) in organic photovoltaic (OPV) devices. Using a lowcost zinc precursor (zinc acetate) in a simple amine-alcohol solvent mix, high-quality ETL thin films are prepared. We show that at a processing temperature of 110 °C the films are composed of nanoparticles embedded in a continuous organic matrix consisting of ZnO precursor species and stabilizers. Using a combination of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), we study the thermally induced morphological and compositional changes in the ETLs. Transient optoelectronic probes reveal that the mixed nanocrystalline/amorphous nature of the films does not contribute to recombination losses in devices. We propose that charge transport in our low-temperature processed ETLs is facilitated by the network of ZnO nanoparticles, with the organic matrix serving to tune the work function of the ETL and to provide excellent resistance to current leakage. To demonstrate the performance of our ETLs we prepare inverted architecture OPVs utilizing Poly[[4, 8-bis[(2-ethylhexyl)oxy]benzo[1, 2-b:4, 5- b′]dithiophene-2, 6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3, 4-b]thiophenediyl]] (PTB7): [6, 6]-Phenyl-C71-butyric acid methyl ester (PC71BM) as active layer materials. The low-temperature ETL devices showed typical power conversion efficiencies (PCEs) of >7% with the champion devices achieving a PCE > 8%.

Original languageEnglish
Pages (from-to)6559-6564
Number of pages6
JournalCrystal Growth and Design
Issue number12
StatePublished - 6 Dec 2017

Bibliographical note

Funding Information:
J.Z. and M.A.M. thank the China Scholarship Council for financial support for PhD studies. K.H. and M.A.M. the National Plan for Science, Technology and Innovation (MAARIFAH) - King Abdulaziz City for Science and Technology - for funding through the Science & Technology Unit at KFUPM award (12-ENE2379-04). D.J.P. acknowledges support from the Royal Society (UF150693) and the EPSRC (EP/M028291/1). M.A.M. and J.R.D. are grateful for continued support through the EPSRC Centre for Doctoral Training in Plastic Electronics (EP/L016702/1).

Publisher Copyright:
© 2017 American Chemical Society.

ASJC Scopus subject areas

  • Chemistry (all)
  • Materials Science (all)
  • Condensed Matter Physics


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