Systematic investigation of organic photovoltaic cell charge injection/performance modulation by dipolar organosilane interfacial layers

Charles Kiseok Song, Alicia C. White, Li Zeng, Benjamin J. Leever, Michael D. Clark, Jonathan D. Emery, Sylvia J. Lou, Amod Timalsina, Lin X. Chen, Michael J. Bedzyk, Tobin J. Marks*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


With the goal of investigating and enhancing anode performance in bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells, the glass/tin-doped indium oxide (ITO) anodes are modified with a series of robust silane-tethered bis(fluoroaryl)amines to form self-assembled interfacial layers (IFLs). The modified ITO anodes are characterized by contact angle measurements, X-ray reflectivity, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, atomic force microscopy, and cyclic voltammetry. These techniques reveal the presence of hydrophobic amorphous monolayers of 6.68 to 9.76 Å thickness, and modified anode work functions ranging from 4.66 to 5.27 eV. Two series of glass/ITO/IFL/active layer/LiF/Al BHJ OPVs are fabricated with the active layer = poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) or poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b'] dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)-carbonyl]thi-eno[3,4-b] thiophenediyl]]:phenyl-C71-butyric acid methyl ester (PTB7:PC 71BM). OPV analysis under AM 1.5G conditions reveals significant performance enhancement versus unmodified glass/ITO anodes. Strong positive correlations between the electrochemically derived heterogeneous electron transport rate constants (ks) and the device open circuit voltage (Voc), short circuit current (Jsc), hence OPV power conversion efficiency (PCE), are observed for these modified anodes. Furthermore, the strong functional dependence of the device response on k s increases as greater densities of charge carriers are generated in the BHJ OPV active layer, and is attributable to enhanced anode carrier extraction in the case of high-ks IFLs.

Original languageEnglish (US)
Pages (from-to)9224-9240
Number of pages17
JournalACS Applied Materials and Interfaces
Issue number18
StatePublished - Sep 25 2013


  • heterogeneous electron transfer rate constant
  • open circuit voltage
  • organic photovoltaics
  • power conversion efficiency
  • self-assembled monolayer
  • work function

ASJC Scopus subject areas

  • General Materials Science


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