Electronic Supporting Information. Harnessing Molecular Photon Upconversion at Sub-Solar Irradiance Using Dual Sensitized Self-Assembled Trilayers

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1 Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is The Royal Society of Chemistry 217 Electronic Supporting Information Harnessing Molecular Photon Upconversion at Sub-Solar Irradiance Using Dual Sensitized Self-Assembled Trilayers Tristan Dilbeck, Sean P. Hill, Kenneth Hanson* Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, 3236, United States Contents 1. Materials...Page S2 2. Photophysical and Electrochemical Measurements...Page S Table S1. Device performance...page S4 4. Table S2. Photophysical properties of A, PtP, and PdP...Page S4 5. Figure S1. Full UV-vis Spectra...Page S5 6. Figure S2. ATR-IR spectra...page S5 7. Figure S3. Emission spectra for PdP and Bilayer...Page S6 8. Figure S4. Interlayer Energy Transfer...Page S6 9. Figure S5. UV-vis Absorption Spectra of Co 2+/3+...Page S7 1. Figure S6. J-V Curves with 375 nm LP Filter...Page S7 11. Figure S7. IPCE of Dual Sensitized Bilayer and Components...Page S8 12. References...Page S9 S1

2 Materials. 4,4'-(anthracene-9,1-diyl)bis(4,1-phenylene) diphosphonic acid (A) 1 Co(phen) 3 (PF 6 ) 2 and Co(phen) 3 (PF 6 ) 3 (Co 3+/2+ ) 2 were prepared by following previously published procedure. Zinc acetate dehydrate, H 2 PtCl 6, nitrosyl tetrafluoroborate, cobalt (II) chloride, ammonium hexafluorophosphate (Sigma-Aldrich), 2,2 bipyridine (Oxchem), Pd(II) meso-tetra(4-carboxyphenyl)porphine (PdP), and Pt(II) meso-tetra(4- carboxyphenyl)porphine (PtP) (Frontier Scientific), were purchased from their respective suppliers, in parentheses, and used without further purification. All other reagents and solvents (analytical reagent grade) have been purchased and used without further purification from VWR. Fluorine-doped tin oxide (FTO) coated glass (sheet resistance 15-1 ) was purchased from Hartford Glass Co. Meltonix film (117-25) and Vac'n Fill Syringe (6529) were purchased from Solaronix. Micro glass cover slides (18 18mm) were obtained from VWR. and sol-gel pastes were prepared following a previously reported procedure. 3-5 Photophysical and Electrochemical Measurements. Energy Transfer Measurements: The efficiency of interlayer energy transfer for -A-Zn- PtP, -A-Zn-PdP and -PdP-Zn-PtP were quantified using steady-state and and time-resolved emission experiments. PtP and PdP were excited at 51 nm and 525 nm, respectively, and emission was measured from 6-8 nm. Emission quenching was calculated using equation S1 where I SA is the integrated emission intensity from 6-8 nm for -A-Zn-PtP, -A-Zn-PdP and -PdP-Zn-PtP, and I S is the emission intensity for -PtP or -PdP. The concentration of sensitizer was the same in the monolayer and bilayer films so there was no need to correct for absorbance differences. S2

3 % h = (1 ) 1 (Eq. S1) Incident Photon to Current Efficiency: IPCE was acquired every 5 nm (5 nm bandwidth) with excitation intensities measured at each wavelength (I ex ) to correct for variation throughout the spectrum. % IPCE was calculated using Equation S2. % = (Eq. S2) Amperometric i t. Data were collected using a CH Instruments CHI63E electrochemical analyzer using a two-electrode configuration ( working, Pt counter) held at V applied potential. The samples were irradiated with either an AM1.5 solar simulator (Light Model oriel corrected with a standard air-mass filter) passing through a 375 nm (to prevent DPPA dimerization, blocks <5% of solar intensity) or 495 nm (to isolate the contribution due to upconversion) long pass filters, or with 532 nm from a Nd:YAG laser (Aixiz, AD T). The intensity of solar irradiance was controlled by varying the distance between the solar simulator source and sample. The laser light intensity was controlled using a neutral density filter as described above for the photophysical measurements. A Model T132 Shutter Driver/Timer (UniBlitz) coupled to a mechanical shutter (Vincent Associates, VS25) was placed between the light source and sample to control 1 s light-dark intervals over a 7 s time period. S3

4 Table S1. Performance characteristics of DSSCs containing dual sensitized bilayers and trilayer photoanodes under AM1.5 irradiation with 375nm and 495 nm long pass filters. Sample Filter (nm) J sc (μa/cm 2 ) V oc (mv) η a (%) -Zn-PtP 5% Zn-PdP 5% < Zn-PtP/PdP Zn-PtP Zn-PdP Zn-PdP-Zn PtP a η = (unflitered incident light power/electrical power output) 1. A PtP PdP Table S2. Photophysical properties of A, PtP, and PdP. λ abs a (nm) (ε, 1 4 M -1 cm -1 ) 358 (.77), 376 (1.27), 397 (1.2) 45 (1.28), 51 (1.3), 54 (.19) 419(14.63), 524 (1.41), 555(.16) λ em b (nm) τ c ( s) Φ k r d (s -1 ) k nr e (s -1 ) E 1/2 ox (V vs NHE) E 1/2 (S 1 ) f E 1/2 (T 1 ) g a Measured in a DMSO solution. b Emission for A, PtP, and PdP on in MeCN. c Lifetime from an exponential tail fit to the excited state decay (ex: 36 (A), 51 (PtP) nm, and 525 (PdP)). d k r = Φ/τ. e k nr = (1-Φ)/τ. f The singlet excited state reduction potential. g The triplet excited state reduction potential. S4

5 Absorbance (a.u.) Absorbance (a.u.) Absorbance (a.u.) a) 2 1 -A -A-Zn-PtP 5% -A-Zn-PdP 5% -A-Zn-PdP/PtP b) A -A-Zn-PtP -A-Zn-PdP -A-Zn-PdP-Zn-PtP Figure S1. UV-vis absorption spectra for (a) the dual sensitized bilayer and components and (b) dual sensitized trilayer and components A-Zn-PdP-Zn-PtP -A-Zn-PdP-Zn -A-Zn-PdP -A-Zn -A Wavenumbers (cm -1 ) Figure S2. ATR-IR spectra throughout the formation of the dual sensitized trilayer (spectra are shifted in the y direction for clarity). S5

6 Intensity (counts) Intensity (counts) 6.x x1 5 3.x1 5 -A-Zn-PdP -A -PdP 1.5x Figure S3. Emission spectra for -A-Zn-PdP (A:PdP, 1:1), -A, and -PdP in argon deaerated MeCN under 532 nm excitation (2.5 W/cm 2 ) Time ( s) -PtP -PdP-Zn-PtP Figure S4. Emission spectra for -PtP and -PdP-Zn-PtP in MeCN excited at 55 nm (inset: time-resolved emission at 67 nm). S6

7 Normalized Absorbance 1..8 Co II (phen) 3 Co III (phen) Figure S6. Normalized UV-vis absorption spectra for Co II (phen) 3 2PF 6 and Co III (phen) 3 3PF 6 in MeCN. a) Current ( A/cm 2 ) A-Zn-PdP/PtP -A-Zn-PdP 5% -A-Zn-PtP 5% b) Current (ma/cm 2 ) A-Zn-PdP-Zn-PtP -A-Zn-PdP -A-Zn-PtP Voltage (mv) Voltage (mv) Figure S6. Photocurrent density-voltage characteristics for DSSCs with photoanodes composed of a) the dual sensitized bilayer and its comparable singly sensitized bilayers and b) the dual sensitized trilayer and its comparable singly sensitized bilayers all with Co 2+/3+ redox mediator in MeCN under AM1.5 irradiation with a 375 nm long-pass filter. S7

8 IPCE (%) Absorptance (%).3.2 Absorptance IPCE PtP/PdP PtP 5% PdP 5% Figure S7. IPCE (filled squares) and absorptance (empty circles) for DSSCs composed of photoanodes of -A-Zn-X where X is indicated in the top right corner of each spectrum. S8

9 References 1. S. P. Hill, T. Banerjee, T. Dilbeck and K. Hanson, J. Phys. Chem. Lett., 215, 6, S. M. Feldt, E. A. Gibson, E. Gabrielsson, L. Sun, G. Boschloo and A. Hagfeldt, J. Am. Chem. Soc, 21, 132, O. O. Ogunsolu, I. A. Murphy, J. C. Wang, A. Das and K. Hanson, ACS Appl. Mater. Interfaces, 216, 8, W. Song, C. R. K. Glasson, H. Luo, K. Hanson, M. K. Brennaman, J. J. Concepcion and T. J. Meyer, J. Phys. Chem. Lett., 211, 2, S.-H. A. Lee, N. M. Abrams, P. G. Hoertz, G. D. Barber, L. I. Halaoui and T. E. Mallouk, J. Phys. Chem. B, 28, 112, S9