Accession Number:

ADA625475

Title:

Supersaturated Self-Assembled Charge-Selective Interfacial Layers for Organic Solar Cells

Descriptive Note:

Journal article

Corporate Author:

NORTHWESTERN UNIV EVANSTON IL DEPT OF CHEMISTRY

Report Date:

2014-11-24

Pagination or Media Count:

13.0

Abstract:

To achieve densely packed charge-selective organosilane-based interfacial layers IFLs on the tin-doped indium oxide ITO anodes of organic photovoltaic OPV cells, a series of Ar 2 N-CH 2 n -SiCl 3 precursors with Ar 3,4 difluorophenyl, n 3, 6, 10, and 18, was synthesized, characterized, and chemisorbed on OPV anodes to serve as IFLs. To minimize lateral nonbonded -NAr 2 Ar 2 N- repulsions which likely limit IFL packing densities in the resulting self-assembled monolayers SAMs, precursor mixtures having both small and large n values are simultaneously deposited. These heterogeneous SAMs are characterized by a battery of techniques contact angle measurements, X-ray reflectivity, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy UPS, cyclic voltammetry, and DFT computation. It is found that the headgroup densities of these supersaturated heterogeneous SAMs SHSAMs are enhanced by as much as 17 versus their homogeneous counterparts. Supersaturation significantly modifies the IFL properties including the work function as much as 16 and real dipole moment as much as 49. Bulk-heterojunction OPV devices are fabricated with these SHSAMs ITOIFLpoly4,8- bis2-ethylhexyloxybenzo1,2- b 4,5- bdithiophene-2,6-diyl2-2-ethylhexyloxycarbonyl-3- fl uorothieno3,4- b thiophenediylphenyl-C 71 -butyric acid methyl ester PTB7PC 71 BMLiFAl. OPVs having SHSAM IFLs exhibit significantly enhanced performance PCE by 54 V oc by 35 due to enhanced charge selectivity and collection, with the PCE rivaling or exceeding that of PEDOTPSS IFL devices 7.62. The mechanism underlying the enhanced performance involves modified hole collection and selectivity efficiency inferred from the UPS data.

Subject Categories:

  • Physical Chemistry
  • Electric Power Production and Distribution
  • Atomic and Molecular Physics and Spectroscopy
  • Solid State Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE