Designed bithiophene-based interfacial layer for high-efficiency bulk-heterojunction organic photovoltaic cells. Importance of interfacial energy level matching

Alexander W. Hains, Charusheela Ramanan, Michael D. Irwin, Jun Liu, Michael R. Wasielewski, Tobin J. Marks

Research output: Contribution to journalArticle

76 Citations (Scopus)


This contribution describes the design, synthesis, characterization, and organic photovoltaic (OPV) device implementation of a novel interfacial layer (IFL) for insertion between the anode and active layer of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C 61- butyric acid methyl ester (PCBM) bulk-heterojunction solar cells. The IFL precursor, 5,5′-bis[(p- trichlorosilylpropylphenyl)phenylamino]- 2,2′-bithiophene (PABTSi 2), covalently anchors to the Sn-doped In 2O 3 (ITO) surface via the - SiCl 3 groups and incorporates a bithiophene unit to align the highest occupied molecular orbital (HOMO) energy with that of P3HT (5.0 eV). The synthesis and subsequent electrochemical analysis of PABTSi 2 indicates a HOMO energy of 4.9 eV, while the lowest uoccupied molecular orbital level remains sufficiently high, at 2.2 eV, to effectively block electron leakage to the OPV ITO anode. For the P3HT:PCBM OPV fabrication, PABTSi 2 is used as a spin-coated cross-linked (via - SiCl 3 hydrolysis and condensation) 1:2 blend with poly[9,9-dioctylfluorene-co-A/-[4- (3- methylpropyl)]-diphenylamine] (TFB). Such devices exhibit an average power conversion efficiency of 3.14%, a fill factor of 62.7%, an open-circuit voltage of 0.54 V, and a short-circuit current of 9.31 mA/cm 2, parameters rivaling those of optimized PEDOT:PSS- based devices.

Original languageEnglish
Pages (from-to)175-185
Number of pages11
JournalACS Applied Materials and Interfaces
Issue number1
Publication statusPublished - Jan 27 2010



  • Electron blocking
  • Interface
  • Organic photovoltaics

ASJC Scopus subject areas

  • Materials Science(all)

Cite this