Supporting Information

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1 Supporting Information Distance Dependence of Plamson-Enhanced Photocurrent in Dye-Sensitized Solar Cells Stacey D. Standridge, George C. Schatz, and Joseph T. Hupp Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL Experimental Methods: Silver Synthesis: Silver NPs were synthesized according to a literature procedure. 1 Briefly, 0.3 g silver oxide was added to 300 ml ultrapure water. The solution was heated to 70ºC. The reaction proceeded for 4 hours under a hydrogen atmosphere. Fluorine-doped tin oxide (FTO) was sonicated for 10 minutes each in soapy water, ethanol, and acetone. The slides were rinsed with isopropanol and dried under flowing nitrogen. Atomic Layer Deposition (ALD, see below) was used to deposit a 100 cycle (~3 nm) base layer of TiO 2. The slides were soaked for 3 hours in a 2 wt. % solution of 4- (polyvinyl)pyridine (2 wt. %) in ethanol. The slides were heated for 1 hour at 100º, then they were soaked in the colloidal silver solution (NP diameter = 36.0 ± 3.2 nm) for 15 hours. ALD: Amorphous TiO 2 was deposited from a titanium isopropoxide (TIP) precursor using a Cambridge Nanotech Savannah 100 ALD system. The chamber temperature and the TIP precursor were held at 200ºC and 80ºC, respectively. The water was at room temperature, and the N 2 flow rate was 20 sccm. The precursors were pulsed for 0.1 s each, and held in the chamber for 1 s followed by a 12 s pump. Clean silicon chips were coated concurrently with the samples to monitor TiO 2 film growth. Roughly 50 nm of silver was deposited onto clean glass slides using an Edward Auto 306 E-Beam evaporator. For selected ALD runs, the growth of the TiO 2 was monitored using both the silicon and the silver substrates. To crystallize the anatase samples, they were annealed under N 2 at 450 ºC for 30 minutes. Slides were soaked in a 0.25 mm solution of N3 dye in ethanol for 12 hours. - S1 -

2 Anode Characterization: The TiO 2 thicknesses on both substrates were measured with a J.A. Woolam Co. M2000 variable angle spectroscopic ellipsometer. All thicknesses were relative to an uncoated wafer, which had a native oxide layer thickness of 28.8 Å. For the same number of cycles, 1.3 times as much TiO 2 grew on silicon substrates as on silver. A full list of the values measured can be found in Table S1. The extinction of the samples was measured with a Cary 5000 UV-Vis-NIR spectrometer. A Hitachi S-4800 SEM was used with a 10.0 kv accelerating voltage to obtain micrographs (Figure S1). AFM experimental method goes HERE Cell Assembly: The platinized back electrode was made by drop-casting 5mM H 2 PtCl 6 in ethanol on clean FTO and heating the substrate to 380 C for 20 minutes in air. The electrodes were sealed together by melting a 60 micron thick surlyn spacer. The redox shuttle was a solution of 0.60 M 3-butyl-3-methylimidazolium iodide, 0.03 M I 2, 0.10 M guanidinium thiocyanate, and 0.50 M 4-tert-butylpyridine in ethanol. It was vacuumloaded into the cells through pre-drilled holes in the platinized substrate, which were sealed closed with a sheet of surlyn and a cover slip. Conductive silver epoxy was used to attach copper leads to each electrode. Cell Measurements: A CH Instruments CHI 1202 Electrochemical Analyzer electrochemical set up was interfaced with a Jovin Yvon Spex FluoroLog-3 fluorimeter to obtain solar cell data. The fluorimeter was calibrated with a light intensity of 100 mw/cm 2 and an AM 1.5 solar filter was used. - S2 -

3 Supplemental Data: ALD TiO 2 Cycles TiO 2 Thickness (nm) TiO 2 Thickness (nm) on Si Substrate on Ag Substrate a Amorphous 125 cycles cycles cycles cycles Anatase 300 cycles cycles cycles cycles a Values were obtained by dividing TiO 2 thickness on Si by 1.3. The factor of 1.3 was obtained by comparing thicknesses measured on analogous silicon and silver NP substrates. Table S1. ALD cycles and corresponding thicknesses of amorphous and anatase TiO 2 on Si and Ag substrates. Figure S1. SEM micrograph of silver NP covered anode before ALD and cell assembly. - S3 -

4 Anode Configuration J sc (µw/cm 2 ) V oc (V) FF Efficiency (%) Dye Silver Dye & Silver 125 Cycles Amorphous E Cycles Amorphous E Cycles Amorphous E Cycles Amorphous E Cycles Anatase E Cycles Anatase E Cycles Anatase E Cycles Anatase E Cycles Amorphous E Cycles Amorphous E Cycles Amorphous E Cycles Amorphous E Cycles Anatase E Cycles Anatase E Cycles Anatase E Cycles Anatase E Cycles Amorphous E Cycles Amorphous E Cycles Amorphous E Cycles Amorphous E Cycles Anatase E Cycles Anatase E Cycles Anatase E Cycles Anatase E-03 Table 2. Solar cell data for cells with 125, 175, 250, and 300 cycles of amorphous TiO 2 and for cells with 300, 350, 400, and 450 cycles of anatase TiO 2. - S4 -

5 Figure S2. Change in vibration frequency of QCMs with the addition of N3 dye to the solution. References: (1) Evanoff, D. D.; Chumanov, G. J. Phys. Chem. B 2004, 108, S5 -