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

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

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
Pages (from-to)9224-9240
Number of pages17
JournalACS Applied Materials and Interfaces
Volume5
Issue number18
DOIs
Publication statusPublished - Sep 25 2013

    Fingerprint

Keywords

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

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Song, C. K., White, A. C., Zeng, L., Leever, B. J., Clark, M. D., Emery, J. D., Lou, S. J., Timalsina, A., Chen, L. X., Bedzyk, M. J., & Marks, T. J. (2013). Systematic investigation of organic photovoltaic cell charge injection/performance modulation by dipolar organosilane interfacial layers. ACS Applied Materials and Interfaces, 5(18), 9224-9240. https://doi.org/10.1021/am4030609