All 118 elements with their physical properties, oxidation states, compounds, reactions and standard reduction potentials. Switch to the energy view to see which elements build solar-cell transport layers, absorbers and electrodes, supercapacitors, batteries, fuel cells, thermoelectrics, CO₂ reduction catalysts, and hydrogen production and storage materials.
Device builder
Choose an electrode, transport layers and absorber to see the energy levels of the whole solar cell stack. The selectors and the diagram both follow the real order of the device, from the front electrode where light enters to the back electrode, and share the same numbers. The check lists each interface and says whether electrons and holes can leave the absorber without a barrier or a large voltage loss.
Interface layers
Insert extra layers anywhere in the stack, for example a BCP buffer under the metal or a 2D perovskite passivation layer. Tick “thin tunnelling layer” for layers of a few nanometres that carriers tunnel through: they are drawn but not treated as a transport barrier.
Add a material
Band edges are in eV against the vacuum level and are negative, for example CB −4.2 and VB −7.5. Work functions are positive.
Material values
Correct any band edge, gap or work function. Changing the gap keeps VB fixed and moves CB. Edited rows are highlighted and each has its own Reset. Changes apply to the device builder only.
| Material | Used as | CB / LUMO (eV) | VB / HOMO (eV) | Gap (eV) | Work function (eV) |
|---|
A screening tool. It lines levels up at the vacuum level and ignores interface dipoles, band bending, doping and defects, which shift real offsets by a few tenths of an eV. Band edges are the same indicative values as in the band alignment chart; the SAM LUMO levels are estimated from an optical gap of about 3.5 eV. The efficiency limit is the Shockley–Queisser value for the absorber gap alone and does not account for the contacts. Advanced options let you add interface layers and your own materials and correct any value; your changes are saved in this browser only.
Stack a wide-gap top cell on a narrow-gap bottom cell. The top cell absorbs the high-energy light and passes the rest down. In a two-terminal tandem the cells are in series, so the smaller of the two currents flows through both and the gaps must be paired to match.
Detailed-balance limits under AM1.5G sunlight at 25 °C: each cell absorbs every photon above its gap that reaches it and loses carriers only by radiative recombination. Luminescent coupling between the cells, reflection and parasitic absorption are ignored. Real tandems reach roughly three quarters of these limits.
A photocatalyst splits water only if its conduction band lies above the H⁺/H₂ level and its valence band lies below the O₂/H₂O level, with a gap small enough to absorb sunlight. Pick a material or enter your own band edges. Select a bar in the chart to check that material.
Indicative band edges at pH 0, where H⁺/H₂ sits at −4.44 eV and O₂/H₂O at −5.67 eV against vacuum. Reported values spread by about ±0.2 eV. The band edges of oxides shift with pH at the same 59 mV per unit as the water levels, so their alignment barely changes; sulfides and nitrides shift less. The efficiency figure assumes every photon above the gap makes hydrogen.
Choose a positive electrode, a negative electrode and an electrolyte. The builder finds the cell voltage from the stable potential window of each electrode, balances the masses so both store the same charge, and estimates capacitance and energy. Every number in the form can be overwritten with your own.
Add your own electrode
Give the capacitance and the stable potential window in each electrolyte type where the electrode works. Leave a pair blank where it is not used. Potentials are in volts against Ag/AgCl.
Your electrodes
A screening estimate. Capacitances, potential windows and the electrolyte limit are typical values that you can overwrite with your own; real windows depend on scan rate, pH and the exact material. Changes typed into the form last until you change the selection; electrodes added under Advanced options are saved in this browser. Energy is per total active mass of both electrodes; a packaged device stores about a quarter to a third of that.
Band alignment of transport layers
Conduction and valence band edges against the vacuum level. An electron transport layer needs its conduction band at or just below the absorber's and a deep valence band to block holes. A hole transport layer needs its valence band at or just above the absorber's and a shallow conduction band to block electrons. Dashed lines mark the MAPbI₃ band edges.
Indicative values. Reported band edges vary by about ±0.3 eV with deposition method, doping and measurement technique.
Redox ladder
Standard reduction potential of each element's main couple, in volts against the standard hydrogen electrode, sorted from the strongest reducing agents to the strongest oxidants. Couples below 0 V can reduce H⁺ to hydrogen. Couples above 1.23 V can oxidise water to oxygen. Select a bar to open the element.
Efficiency limit against band gap
The Shockley–Queisser limit: the highest efficiency a single-junction solar cell can reach for a given band gap under standard sunlight. It peaks at 33.7 % near 1.34 eV. A smaller gap loses voltage; a larger gap absorbs less light. The dots place the absorbers of the band alignment chart on the curve.
Calculated from the ASTM G173 AM1.5G spectrum by detailed balance at 25 °C, with radiative recombination only and emission from the front surface. Real cells fall below it.
Ragone plot
Specific energy against specific power for the main storage technologies. Supercapacitors deliver high power for seconds, batteries store more energy and release it over minutes to hours, and fuel cells run for as long as hydrogen is supplied. Dashed lines mark equal discharge time.
Indicative cell-level ranges drawn from typical literature values. Packaged systems are lower.
Hydrogen storage map
Hydrogen content by weight against hydrogen density by volume. The best materials sit toward the top right. The points are for the material alone, while the US Department of Energy targets are for a complete storage system including tank, valves and heat exchange, so a material must beat the target by a wide margin.
Theoretical capacities from formula weight and crystal or liquid density. Reversible capacity and working temperature differ: see the materials tab.
Hydrogen evolution volcano
Catalytic activity for hydrogen evolution against how strongly the surface binds hydrogen. The best catalysts sit at the top, where the binding energy is close to zero: platinum-group metals and, among cheap materials, the edges of MoS₂. Select a metal to open the element.
Approximate values after Nørskov et al., J. Electrochem. Soc. 2005 and Jaramillo et al., Science 2007. The dashed line is a guide to the eye.
Candidate materials
Property plot
Plot any two numeric properties against each other. The role filter above also applies here.
Select a material name to open its page. Column headers sort the table. Numbers used for filtering, sorting and plotting are read automatically from the key figures; a few are theoretical maxima, and a range counts as a match when any part of it falls inside your limits. Elements outlined in red are on the EU 2023 list of critical raw materials. Sources: named papers are landmark or review references whose DOI was checked against Crossref; they support the material's role, not every figure in the row. “Search literature” opens a Google Scholar search for the material.
Compare elements
Put up to three elements side by side. Adding a fourth replaces the oldest.
Calculators
Quick calculations for the lab. Results update as you type.
Supercapacitor from a discharge curve (GCD)
Supercapacitor from a CV curve
Battery theoretical capacity
Q = n·F / (3.6·M). Brackets and decimals work, for example LiNi0.8Co0.15Al0.05O2 or Na3V2(PO4)3 with 2 electrons.
Water electrolysis
Two electrons per H₂ molecule (Faraday's law). Efficiency compares the cell voltage with the thermoneutral 1.48 V or the 1.25 V lower-heating-value equivalent.
Solar cell efficiency limit
Shockley–Queisser limit under AM1.5G sunlight for a single junction.
Unit converters
Contact
Found an error, a broken link or a value that needs updating, or want a material added? Please write to:
Prof. E. Shalaan
eshalan@kau.edu.sa · eshalaan@gmail.com