Solar Fuels Modeling Website

It is recommended that the water depth value is maintained since the matching photoabsorber (to your photoelectrode) probably still needs to account for water absorption

Concentration: times AM1.5

Photoabsorber Options

Absorbs: % of the incoming photons above its band gap

Absorption coefficient 1/cm (Assumes uniform attenuation)
Photoabsorber thickness µm

Absorbs: % of the incoming photons above its band gap

Absorption coefficient 1/cm (Assumes uniform attenuation)
Photoabsorber thickness µm

The user should consider any parasitic light absorption from the top cell at photon energies below the band gap and adjust the bottom cell absorption % to compensate. (A simple UV-Vis of the top photoabsorber can determine parasitic absorption.)

The band gap of the photoabsorber used in the CV is: mV
The photoelectrode in the CV is the:
The photoelectrode in the CV is doing a/an
Select the .csv file that contains the CV of the photoelectrode (formatting):
--Here is an example file of a Si photocathode data file based very roughly on the work by Seger et.al, JACS, 2014--

The file should contain only 2 columns with no headers.
Column 1 should be the voltage (V) and column 2 should be the current in (mA/cm²).
The file should be only a single linear sweep across the voltage range.
Scan rate does not matter.
The voltage should be versus the redox reaction being done (i.e. (vs. RHE) for H₂, vs (1.23 V vs RHE) for O₂ evolution).
Voltage example: if one is operating at 0.8V vs. RHE for O₂ evolution, this would need to be inputted as +0.42 V.
When it doubt about the voltage sign, more positive voltages are good, negative voltages are bad.
The voltage needs to be in ascending or descending order (thus 0.1, 0.2. 0.3 V) not (0.1, 0.3, 0.2 V). Very rarely should this ever be an issue.
The sign (+/-) of the current does not matter. The program takes the absolute value of the current.
If your CV slightly crosses over the 0-current axis, these points will be cropped out/eliminated. (This is done by eliminating all points that do not have the same sign as the maximum)
The programs assumes the file is done under AM1.5 light.
The program also assumes any losses due to ion transfer have been compensated for
Water primarily absorbs in the low band gap regime. Thus the user should make a educated decision when setting the water absorption depth with respect to their experiment and the band gap of their photoabsober.

Dark saturation current (mutiple of theoretical minimum) (?): x

The minimum theoretical dark saturation current (i_{o, theory}) is a function of band gap, temeparture as given by : Martin A. Green "Third Generation Photovoltaics" (Springer, Heidelberg 2003) page 38. This multiplier will take i_{o, theory} and multiply it by whatever constant is set here.
Example: if the calculations determines i_{o, theory} for a 1.0 eV band gap mateial is 10^-11 mA/cm² and the multiplier is 100, the program will use a i_o=10^-9 mA/cm²

Determine dark saturation current through a set open circuit value This approach is based off of the work from Seitz et al. ChemSusChem, 2014
Assume the open circuit voltage of the photoabsorber has a band gap of mV less than the band gap. The program will then calculate a dark saturation current based off of this value.

Shunt resistance Ohm x cm²
Series resistance Ohm x cm²
Force a set fill factor (by modifying the series resistance)      Force a fill factor value of % for each photoabsorber
     Force a tandem solar cell fill factor value of %
     The tandem solar cell approach is based off the work of Hu et al., 2013, Energy & Environmental Science.
The maximum fill factor is limited by bandgap. If the set fill factor is greater than the maximum theoretical fill factor, the program will leave this point blank since it is unfeasible.

This approach is based of the work of Hu et. al, Energy & Environmental Science, 2013

Thermodynamic potential of the reaction mV

--This assumes equal molar concentration of reactants and products--
Enthalpy of reaction kJ/mol
Entropy of reaction J/(mol K)
Number of electrons transferred per reaction

There should be no reduction overpotential since the user generated CV has taken this into account (unless the CV is a pure photovoltaic)

Overpotential from the reduction reaction mV

Select the .csv file that contains the linear sweep of the reduction reaction (formatting):
--Here is an example file of low loading (200ng/cm²) Pt for H₂ reduction based on the electrocatalyst used in the work from Kemppainen et.al, EES, 2015--

The file should contain only 2 columns with no headers.
Column 1 should be the overpotential (in mV) and column 2 should be the current in (mA/cm²).
The file should be only a single linear sweep across the voltage range.
Scan rate does not matter.
It does not matter whether the current is positive or negative.
The program interpolates data, but does not extrapolate the i-V curve.

Tafel slope for reductive reaction mV/decade
Exchange current density mA/cm²

Overpotential at 1 mA/cm² mV
Tafel slope for reductive reaction mV/decade

There should be no oxidation overpotential since the user generated CV has taken this into account (unless the CV is a pure photovoltaic)

Overpotential from the oxidation reaction mV

Tafel slope for oxidative reaction mV/decade
Exchange current density mA/cm²

Overpotential at 1 mA/cm² mV
Tafel slope for oxidative reaction mV/decade

Select the .csv file that contains the linear sweep of the reduction reaction (formatting):
--Here is an example file of a RuO₂ electrocatalyst for O₂ evolution based on the work by Frydendal et.al, ChemeEectroChem, 2014--

Ionic loss between anode and cathode mV

Ionic conductivity mS/cm
Average ionic path length cm

Elecrolyte
Concentration (molarity)

Average ionic path length cm

Precision Options
If you set the values too accurate or precise you may freeze your computer for a little bit (or longer), while it is doing the calculations.

The program calculates efficiencies conservatively (via iteration process), thus increasing the precision may yield a slight increase in efficiency.

Precision Efficiency
Current step size (?): in µA/cm²

The program iterates through current to find the maximum current/efficiency for the device. This is how big the step size is between iterations.

Photoabsorbers
Top cell photoabsorber band gap range: From meV to meV
with data points every: meV

Bottom cell photoabsorber band gap range: From meV to meV
with data points every: meV

i-V curve
For each band gap an i-V curve is made and then the voltage is varied to find the maximum current (and hence efficiency) for a given reaction.
Current precision in i-V curve: ( x Current step size) in µA/cm²
Voltage precision in i-V curve: in mV

If you are interested in seeing a pure photovoltaic type i-V curve (?), for a given band gap of eV,

This uses the light concentration, water absorption, photoabsorber absorption (from top cell), dark saturation current (multiple of theoretical minimum), series and shunt resistance to create an i-V curve.

Plot Options

Options for Single Photoabsorber and Plots involving User Inputted Photoelectrode
Contour Plot Options

Recent Publications Using This Program

Photon-Driven Nitrogen Fixation: Current Progress, Thermodynamic Considerations, and Future Outlook Medford A.J. ; Hatzell M.C. ACS Catalysis 2017 7 (4), 2624–2643 doi: 10.1021/acscatal.7b00439
A Flexible Web-Based Approach to Modeling Tandem Photocatalytic Devices. Seger B.; Hansen, O.; Vesborg P.C.K. Solar RRL 2017 1, 1600013. doi: 10.1002/solr.201600013
Vesborg P.C.K.; Seger B. Performance Limits of Photoelectrochemical CO₂ Reduction Basedon Known Electrocatalysts and the Case for Two-Electron Reduction Products Chemistry of Materials 2016, 28, 8844−8850. doi:10.1021/acs.chemmater.6b03927
Mei B.; Mul G.: Seger B. Beyond Water Splitting: Efficiencies of Photo-Electrochemical Devices Producing Hydrogen and Valuable Oxidation Products Advanced Sustainable Systems 2017 1, 1600035. doi:10.1002/adsu.201600035

Solar Fuels Modeling Website Version 1.1, Please cite (A Flexible Web-Based Approach to Modeling Tandem Photocatalytic Devices, Seger, B., Hansen, O., Vesborg, P.C.K., Solar RRL, DOI:10.1002/solr.201600013) when using this mode. The program was optimized for Firefox, but should work on all major browsers. Brian Seger was the sole programmer of this model, thus pleas contact him for any questions or issues relating to the model here . Read more about the web-based model here.
General Conditions (Always uses an AM1.5 spectrum) Reactor temperature : K It is recommended that the water depth value is maintained since the matching photoabsorber (to your photoelectrode) probably still needs to account for water absorption Water depth (?): cm How much water the light needs to penetrate through before it reaches the photoabsorber(s): (For tandem devices: Only bottom cell is affected by water absorption (?): ) Only click this for tandem devices where the irradiation side of the top cell photoabsorber never sees electrolyte. If this option is used it will assume the electrolyte will be between the top cell photoabsorber and bottom cell photoabsorbers. This approach is not common. If this option is used for single photoabsorbers, it will equivalent to setting the water depth = 0 cm. Concentrator cell (?): This is the light concentraion of the AM1.5 spectra. For light concentrations above 1.00, AM1.5 (Direct + Circumsolar) is used since this spectrum is meant for concentrator cells. For no light concentration (i.e. Concentration = 1) AM1.5 Global is used. For light concentration between 0 and 1, the program uses a given fraction of the AM1.5 Global spectra. The precision to which the program calculates current is automatically adjusted to account for concentration. One can readjust this if desired by clicking on the 'Precision and Ploting' option. Concentration: times AM1.5 Optimize by allowing for additional bias to be used (?): This adds additional bias to the device which helps the photovoltage overcome the thermodynamics and losses of the system. This additional energy used in creating the bias is subtracted off when the efficiency is calculated. Please realize bias here relates to a 2-electrode device, and should not be confused with bias from a 3-electrode device. Ohmic resistance (?): Ohm x cm² This will normally be zero unless you have a wired device or have unconductive protection layers Photoabsorber Options Click to modify light absorption parameters The user should consider any parasitic light absorption from the top cell at photon energies below the band gap and adjust the bottom cell absorption % to compensate. (A simple UV-Vis of the top photoabsorber can determine parasitic absorption.) The file should contain only 2 columns with no headers. Column 1 should be the wavelength (nm) and column 2 should be the Absorbance. (Absorbance is a unitless value. Even though Wikipedia says that Absorbance can in the units of 'A.U' for absorbance units, this is just garbage. 'Absorbance units' was just a cover for people who errently thought Absorbance was just an arbitray number. Rant over.) Scan rate does not matter. 'incoming' is defined as only the photons that have already made it past any water layer that may be present. If photon matching is used the absorption percentage may decrease if the large band gap needs to be thinned down to allow more light penetration to the small band gap material. This is only relevant for tandem devices or situations in which the user uploads a large band gap photoabsober. 'incoming' is defined as only the photons that have already made it past any water layer that may be present and past the photoabsorber #1 . If photon matching is used this value corresponds to an absolute absorption percentage of incident above band gap photons rather than a pro-rated absorption percentage. The band gap of the photoabsorber used in the CV is: mV The photoelectrode in the CV is the: The photoelectrode in the CV is doing a/an Select the .csv file that contains the CV of the photoelectrode (formatting): --Here is an example file of a Si photocathode data file based very roughly on the work by Seger et.al, JACS, 2014-- The file should contain only 2 columns with no headers. Column 1 should be the voltage (V) and column 2 should be the current in (mA/cm²). The file should be only a single linear sweep across the voltage range. Scan rate does not matter. The voltage should be versus the redox reaction being done (i.e. (vs. RHE) for H₂, vs (1.23 V vs RHE) for O₂ evolution). Voltage example: if one is operating at 0.8V vs. RHE for O₂ evolution, this would need to be inputted as +0.42 V. When it doubt about the voltage sign, more positive voltages are good, negative voltages are bad. The voltage needs to be in ascending or descending order (thus 0.1, 0.2. 0.3 V) not (0.1, 0.3, 0.2 V). Very rarely should this ever be an issue. The sign (+/-) of the current does not matter. The program takes the absolute value of the current. If your CV slightly crosses over the 0-current axis, these points will be cropped out/eliminated. (This is done by eliminating all points that do not have the same sign as the maximum) The programs assumes the file is done under AM1.5 light. The program also assumes any losses due to ion transfer have been compensated for Water primarily absorbs in the low band gap regime. Thus the user should make a educated decision when setting the water absorption depth with respect to their experiment and the band gap of their photoabsober. Photovoltage Dark saturation current (mutiple of theoretical minimum) (?): x The minimum theoretical dark saturation current (i_{o, theory}) is a function of band gap, temeparture as given by : Martin A. Green "Third Generation Photovoltaics" (Springer, Heidelberg 2003) page 38. This multiplier will take i_{o, theory} and multiply it by whatever constant is set here. Example: if the calculations determines i_{o, theory} for a 1.0 eV band gap mateial is 10^-11 mA/cm² and the multiplier is 100, the program will use a i_o=10^-9 mA/cm² Determine dark saturation current through a set open circuit value Shunt resistance Ohm x cm² Series resistance Ohm x cm² Force a set fill factor (by modifying the series resistance) This approach is based of the work of Hu et. al, Energy & Environmental Science, 2013 Set photovoltage as function of band gap - absolute (?) mV This assumes the photoabsorber photovoltage is whatever band gap it is minus a set voltage loss irrespective of current. Example: If the loss is set to 500 mV, then the photovoltage for a 1.5 eV band gap photoabsorber will be 1000 mV independent of the current running through the device (up until the limiting current that is set by the band gap) Photovoltage is % of band gap (?) This assumes the photoabsorber photovoltage is a certain percentage of the band gap irrespective of current. Example: If percent is set to 75%, then the photovoltage for a 1.0 eV band gap photoabsorber will be 750 mV independent of the current running through the device (up until the limiting current that is set by the band gap)	Reaction Thermodynamic potential of the reaction mV --This assumes equal molar concentration of reactants and products-- Enthalpy of reaction kJ/mol Entropy of reaction J/(mol K) Number of electrons transferred per reaction Faradaic efficiency = % Calculate production rates (mol/m²/hr) instead of efficiency Reduction Overpotential There should be no reduction overpotential since the user generated CV has taken this into account (unless the CV is a pure photovoltaic) Overpotential from the reduction reaction mV Select the .csv file that contains the linear sweep of the reduction reaction (formatting): --Here is an example file of low loading (200ng/cm²) Pt for H₂ reduction based on the electrocatalyst used in the work from Kemppainen et.al, EES, 2015-- The file should contain only 2 columns with no headers. Column 1 should be the overpotential (in mV) and column 2 should be the current in (mA/cm²). The file should be only a single linear sweep across the voltage range. Scan rate does not matter. It does not matter whether the current is positive or negative. The program interpolates data, but does not extrapolate the i-V curve. Tafel slope for reductive reaction mV/decade Exchange current density mA/cm² Overpotential at 1 mA/cm² mV Tafel slope for reductive reaction mV/decade Oxidation Overpotential There should be no oxidation overpotential since the user generated CV has taken this into account (unless the CV is a pure photovoltaic) Overpotential from the oxidation reaction mV Tafel slope for oxidative reaction mV/decade Exchange current density mA/cm² Overpotential at 1 mA/cm² mV Tafel slope for oxidative reaction mV/decade Select the .csv file that contains the linear sweep of the reduction reaction (formatting): --Here is an example file of a RuO₂ electrocatalyst for O₂ evolution based on the work by Frydendal et.al, ChemeEectroChem, 2014-- The file should contain only 2 columns with no headers. Column 1 should be the overpotential (in mV) and column 2 should be the current in (mA/cm²). The file should be only a single linear sweep across the voltage range. Scan rate does not matter. It does not matter whether the current is positive or negative. The program interpolates data, but does not extrapolate the i-V curve. Ionic Losses Ionic loss between anode and cathode mV Ionic conductivity mS/cm Average ionic path length cm Elecrolyte Concentration (molarity) Average ionic path length cm
Precision and Plotting Options: Precision Options If you set the values too accurate or precise you may freeze your computer for a little bit (or longer), while it is doing the calculations. The program calculates efficiencies conservatively (via iteration process), thus increasing the precision may yield a slight increase in efficiency. Precision Efficiency Current step size (?): in µA/cm² The program iterates through current to find the maximum current/efficiency for the device. This is how big the step size is between iterations. Photoabsorbers Top cell photoabsorber band gap range: From meV to meV with data points every: meV Bottom cell photoabsorber band gap range: From meV to meV with data points every: meV i-V curve For each band gap an i-V curve is made and then the voltage is varied to find the maximum current (and hence efficiency) for a given reaction. Current precision in i-V curve: ( x Current step size) in µA/cm² Voltage precision in i-V curve: in mV If you are interested in seeing a pure photovoltaic type i-V curve (?), for a given band gap of eV, This uses the light concentration, water absorption, photoabsorber absorption (from top cell), dark saturation current (multiple of theoretical minimum), series and shunt resistance to create an i-V curve.	Plot Options Options for Single Photoabsorber and Plots involving User Inputted Photoelectrode Title: Title Font Size: X-Axis title: Y-Axis title: Font size of axis title: X-Axis tick spacing: eV Y-Axis tick spacing: % Tick Font Size: Fix set values for x-axis Starting band gap (in eV): Ending band gap: eV Fix set values for y-axis Starting efficiency (or produciton rate): % Ending efficiency (or produciton rate): % Contour Plot Options Title: Title font size: X-Axis title: Y-Axis title: : Font size of axis title: X-Axis tick spacing: eV Y-Axis tick spacing: eV Tick font size: Smoothing factor for the contour plots (?) The smoothing factor just makes the graph look good. It does not effect the calculate efficiencies at all. Between 0-1 is suggested, but it possible to go to higher values. Note: that the x and y-axis will be set by the band gap range Fix set values for contour plot Starting efficiency (or produciton rate): % Ending efficiency (or produciton rate): % Interval betwene difference colors: % Color Scheme:

Panel 1: (?) This allows for you to add an extra trace to the graph (x-y plot) or subtract from a previous graph (for contour plots) This either adds or subtracts data to the previous data set irrespective of whether it is on Panel 1 or Panel 2 It is however possible to create new data on one panel and subtract this new data from the previous data on the other panel.	Panel 2: (?) Recent Publications Using This Program Photon-Driven Nitrogen Fixation: Current Progress, Thermodynamic Considerations, and Future Outlook Medford A.J. ; Hatzell M.C. ACS Catalysis 2017 7 (4), 2624–2643 doi: 10.1021/acscatal.7b00439 A Flexible Web-Based Approach to Modeling Tandem Photocatalytic Devices. Seger B.; Hansen, O.; Vesborg P.C.K. Solar RRL 2017 1, 1600013. doi: 10.1002/solr.201600013 Vesborg P.C.K.; Seger B. Performance Limits of Photoelectrochemical CO₂ Reduction Basedon Known Electrocatalysts and the Case for Two-Electron Reduction Products Chemistry of Materials 2016, 28, 8844−8850. doi:10.1021/acs.chemmater.6b03927 Mei B.; Mul G.: Seger B. Beyond Water Splitting: Efficiencies of Photo-Electrochemical Devices Producing Hydrogen and Valuable Oxidation Products Advanced Sustainable Systems 2017 1, 1600035. doi:10.1002/adsu.201600035