Supporting Information

Transcription

1 Supporting Information Red-absorbing Cationic Acceptor Dyes for Photocathodes in Tandem Solar Cells. Christopher J. Wood, a Ming Cheng, b Charlotte A. Clark, a Raphael Horvath, a Ian P. Clark, c Michelle L. Hamilton, a,d Michael Towrie, c,d Michael W. George, a,d Licheng Sun, b Xichuan Yang,* b Elizabeth A. Gibson* a a School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK. b DUT-KTH Joint Research Centre on Molecular Devices, State Key Laboratory of Fine Chemicals, Dalian University of Technology (DUT), Dalian, China.. Sun is also at the Centre for Molecular Devices, Department of Chemistry, School of Chemical Science and Engineering, Royal Institute of Technology (KTH), Stockholm, Sweden. c Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, OX11 0QX, UK. d Dynamic Structural Science Consortium, Research Complex at Harwell, Didcot, Oxfordshire, OX11 0FA UK. Contents 2 Mass Spectrometry 4 Absorption Spectra 4 DFT calculations 7 Electrochemistry 9 p-type Dye Sensitised Solar Cells 10 Spectroelectrochemistry 12 Time-resolved absorption spectroscopy 14 n-type Dye Sensitised Solar Cells

2 Mass Spectrometry Figure S1. ESI + TOF MS of CAD 1 (top) and predicted ESI + TOF MS for CAD1 (bottom). Meas. err err # Formula Score m/z m/z [mda] [ppm] msigma C 41 H 41 N 2 O 2 S C 41 H 42 N 2 O 2 S C 41 H 45 N 3 O 2 S n.a C 41 H 45 N 2 NaO 2 S n.a. Table S1. Results from ESI + TOF MS of CAD 1.

3 Figure S2. ESI + TOF MS of CAD 2 (top) and predicted ESI + TOF MS for CAD 2 (bottom). Meas. err err # Formula Score m/z m/z [mda] [ppm] msigma C 59 H 69 N 2 O 4 S C 59 H 73 N 3 O 4 S n.a C 59 H 69 N 2 NaO 4 S n.a. Table S2. Results from ESI + TOF MS of CAD 2.

4 Absorbance (a.u.) Absorption Spectra Wavelength (nm) Figure S3. Absorption spectra of CAD 1 (circles) and CAD 2 (triangles) adsorbed onto NiO films used in the devices DFT calculations Dyes CAD 1 CAD 2 Transition λ (nm) Oscillator Strength Contribution HOMO LUMO % HOMO-1 LUMO % HOMO LUMO % HOMO LUMO % HOMO-1 LUMO % HOMO-2 LUMO % HOMO-2 LUMO % Table S3. TDDFT data for CAD 1 & CAD 2, calculations were done using DFT B3LYP 6-31G (d) (Default Solvation: CH 2 Cl 2 ).

5 Oscilator Strength Dyes CAD 1 CAD 2 Transition λ (nm) Oscillator Strength Contribution HOMO LUMO % HOMO-1 LUMO % HOMO LUMO % HOMO LUMO % HOMO LUMO % HOMO LUMO % HOMO-1 LUMO % HOMO-2 LUMO % HOMO-2 LUMO % Table S4. TDDFT data for CAD 1 & CAD 2, calculations were done using DFT B3LYP 6-31G + (d) (Default Solvation: CH 2 Cl 2 ) Wavelength (nm) Figure S4. A comparison of predicted absorption peaks for CAD 1 (circles) and CAD 2 (triangle) using 6-31G (d) (black) and 6-31G + (d) (red)

6 LUMO LUMO HOMO HOMO HOMO-1 HOMO-1 HOMO-2 Figure S5. Isodensity plots of the frontier orbitals of CAD 1 (left) and CAD 2 (right).

7 Electrochemistry i ( A) Voltage (V) Figure S6. DPV for the reduction of CAD 1 measured in dichloromethane with 100 mm Bu 4 NClO 4 as electrolyte (working electrode: glassy carbon; reference electrode: Ag/Ag + ; calibrated with ferrocene/ferrocenium (Fe(Cp) 2 +/0 ) as an internal reference, counter electrode: platinum wire.) i ( A) Voltage (V) Figure S7. DPV for the oxidation of CAD 1 measured in dichloromethane with 100 mm Bu 4 NClO 4 as electrolyte (working electrode: glassy carbon; reference electrode: Ag/Ag + ; calibrated with ferrocene/ferrocenium (Fe(Cp) 2 +/0 ) as an internal reference, counter electrode: platinum wire)

8 i ( A) Voltage (V) Figure S8. DPV for the reduction of CAD 2 measured in dichloromethane with 100 mm Bu 4 NClO 4 as electrolyte (working electrode: glassy carbon; reference electrode: Ag/Ag + ; calibrated with ferrocene/ferrocenium (Fe(Cp) 2 +/0 ) as an internal reference, counter electrode: platinum wire) i ( A) Voltage (V) Figure S9. DPV for the oxidation of CAD 2 measured in dichloromethane with 100 mm Bu 4 NClO 4 as electrolyte (working electrode: glassy carbon; reference electrode: Ag/Ag + ; calibrated with ferrocene/ferrocenium (Fe(Cp) 2 +/0 ) as an internal reference, counter electrode: platinum wire)

9 Charge Lifetime(s) Charge Lifetime (s) p-type Dye Sensitised Solar Cells 4 Photocurrent Density (ma cm -2 ) Photovoltage (V) Figure S10. Comparison current-voltage characteristics of the dye-sensitized NiO solar cells using CAD 1 (circles) and CAD 2 (triangles) under AM 1.5G (100 mw cm 2 ) illumination with 3 layers NiO Photovoltage (mv) Charge Density (mc cm -2 ) Figure S11. Comparison of charge lifetimes for CAD 1 (circles), CAD 2 (triangles) and P1 (squares) vs. V OC (left) and extracted charge (Q OC ) (right).

10 Absorbance (a.u) Charge Density (mc cm -2 ) Photovoltage (mv) Figure S12. Q oc vs V oc plot for CAD 1 (circles), CAD 2 (triangles) and P1 (squares) recorded using an Ivium CompactStat potentiostat and an Ivium modulight light source. Spectroelectrochemistry Wavelength (nm) Figure S13. Difference absorption spectra for CAD 1 (circles) CAD 2 (triangles) at an applied voltage of 1.6 V vs. Fe(Cp) +/0 2 ; spectra were measured in dichloromethane with 0.4 M Bu 4 NPF 6 as the supporting electrolyte (working electrode: FTO glass (TEC 15); counter electrode: platinum wire; reference electrode: Ag wire; calibrated with Fe(Cp) +/0 2 as an internal reference. We note that this is at higher wavelength than observed in the TA but the peaks are strongly solvatochromic and blue shift considerably in the presence of electrolyte as shown in Figures S14 and 15.

11 Extinction Coefficient (L mol -1 cm -1 ) Normalised Absorption (a.u) Wavelength (nm) Figure S14. Absorption spectra of CAD 1 in dichloromethane (line) and dichloromethane M Bu 4 NPF 6 (circles) showing the hypsochromic shift in the presence of electrolyte Wavelength (nm) Figure S15. Absorption spectra of CAD 2 in dichloromethane (line) and dichloromethane M Bu 4 NPF 6 (triangles) showing the hypsochromic shift in the presence of electrolyte.

12 Normalised Absorbance Time-resolved absorption spectroscopy Table S5 Table containing the values of the mono-exponential lifetimes (in ps) that have been fitted to data obtained from both TA and TRIR measurements of CAD1 and CAD2 in dichloromethane. TA TRIR Dye λ / nm Lifetime / ps ν(c=o) / cm -1 Lifetime / ps CAD (± 10) (± 30) CAD (± 1) (± 5) 623 nm bi-exp. fit 623 nm 505 nm bi-exp. fit 505 nm 860 nm bi-exp. fit 860 nm Time / ps Figure S16. Kinetic traces measured for decay of transient bands at 505 nm and 860 nm and recovery of parent bleach at 623 nm of CAD 1 adsorbed onto NiO following 532 nm photolysis. Laser energy = 50 nj. Lifetimes fitted as a bi-exponential function.

13 Dye τ of[cad] peak τ of CAD bleach τ of NIR peak (λ = 505 nm) / ps (λ = 623 nm) / ps (λ = 860 nm) / ps Laser power = 50 nj CAD1 (fast) 70 (±) (± 15) 70 (± 60) CAD1 (slow) 2100 (± 360) 2340 (± 340) 900 (± 500) Amplitude weighted τ CAD2 (fast) 25 (± 15) 65 (± 15) (-) CAD2 (slow) 510 (± 150) 730 (± 190) (-) Amplitude weighted τ (-) Laser power = 200 nj CAD1 (fast) 70 (± 20) 85 (± 10) 70 (± 20) CAD1 (slow) 1300 (± 500) 1000 (± 160) 890 (± 180) Amplitude weighted τ CAD2 (fast) 60 (± 5) 30 (± 5) 75 (± 35) CAD2 (slow) 735 (± 70) 650 (± 60) 2800 (± 880) Amplitude weighted τ Laser power = 500 nj CAD1 (fast) 70 (± 10) 75 (± 10) (-) CAD1 (slow) 1900 (± 330) 1600 (± 290) (-) Amplitude weighted τ (-) CAD2 (fast) 50 (± 25) 65 (± 10) (-) CAD2 (slow) 270 (± 150) 940 (± 170) (-) Amplitude weighted τ (-) Table S6. Table containing the values of the bi-exponential lifetimes (in ps) that have been fitted to data obtained from the TA measurements of CAD1 and CAD2 adsorbed to NiO at several points. The average lifetime has been calculated by using the amplitude-weighted method by Smeigh et al., referred to in the main text.

14 n-type Dye Sensitised Solar Cells 0.5 Photocurrent Density (ma cm -2 ) Photovoltage (V) Figure S17. Dark Currents on TiO 2 for P1 (squares) CAD 1 (circles) CAD 2 (triangles) and Blank TiO 2 (Open Circles). 9 Photocurrent Density (ma cm -2 ) Photovoltage (V) Figure S18.. Current-voltage plots for TiO 2 n-dscs illuminated with 100 mw cm 2 AM1.5 light sensitized with P1 (squares) CAD 1 (circles) CAD 2 (triangles).

15 Dyes J SC V OC FF η (ma cm -2 ) (V) % (%) CAD CAD P Table S7. Photovoltaic Performance of TiO 2 n-dscs. Photocurrent Density (ma cm -2 ) 6 CAD 1 CAD 1 Dark Current 5 CAD 2 CAD 2 Dark Current 4 P1 3 P1 Dark Current Photovoltage (V) Figure S19. Current-voltage plots for p-dscs illuminated with 100 mw cm 2 AM1.5 light (filled symbols) and in the dark (open symbols) sensitized with P1 (red triangles) CAD 1 (purple circles) CAD 2 ( blue triangles).