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Title: Can nitro groups really anchor onto TiO 2? Case study of dye-to-TiO 2 adsorption using azo dyes with NO 2 substituents

The nitro group has recently been suggested as a new type of anchor for dye-sensitized solar cells (DSSCs) and has shown promising optoelectronic properties. Considering the excellent electron withdrawing ability of the nitro group and wider materials selection brought about by this substituent, it is helpful to evaluate the interfacial structures and photophysics of more organic dyes where NO 2 poses as the dye-to-TiO 2 anchor. A computational study on a family of azo dyes bearing a nitro group is presented in this paper, where the effect of certain side groups on their optical properties is examined. Both isolated dye molecules and dye/TiO 2 nanocomposites are studied via density functional theory and time-dependent density functional theory, with complementary experimental UV/vis absorption spectroscopy and photovoltaic device testing. Results demonstrate that these nitro-containing dyes prefer a monodentate anchoring mode on a TiO 2 cluster. These nitro dyes reveal weak, but non-negligible, adsorption onto TiO 2; yet, very low photovoltaic performance once incorporated into a DSSC device. Finally, this poor delivery of nitro groups as DSSC anchors is ostensibly inconsistent with previous findings; but is rationalized via the “auxiliary anchor” concept.
Authors:
 [1] ;  [2]
  1. Nanjing Univ. of Information Science and Technology (China). Dept. of Physics; Univ. of Cambridge (United Kingdom). Cavendish Lab.
  2. Univ. of Cambridge (United Kingdom). Cavendish Lab. Dept. of Chemical Engineering and Biotechnology; Argonne National Lab. (ANL), Argonne, IL (United States); STFC Rutherford Appleton Lab., Didcot (United Kingdom). ISIS Neutron and Muon Facility
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 18; Journal Issue: 28; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States); Univ. of Cambridge (United Kingdom); Nanjing Univ. of Information Science and Technology (China)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Engineering and Physical Sciences Research Council (EPSRC); Nanjing Univ. of Information Science and Technology (China)
Contributing Orgs:
STFC Rutherford Appleton Lab., Didcot (United Kingdom)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 14 SOLAR ENERGY; Azo; DFT; Dye-sensitized solar cell; Nitro; Optoelectric material; TDDFT
OSTI Identifier:
1352676