Shockley–Queisser limit

In <a href="/facts/Physics/a7aH2y08">physics</a>, the radiative efficiency limit (also known as the detailed balance limit, Shockley–Queisser limit, Shockley Queisser Efficiency Limit or SQ Limit) is the maximum theoretical <a href="/facts/Efficiency_of_a_solar_cell/Au9KQeed">efficiency of a solar cell</a> using a single <a href="/facts/P%25E2%2580%2593n_junction/CaKIdLPg">p–n junction</a> to collect power from the cell where the only loss mechanism is radiative recombination in the solar cell. It was first calculated by <a href="/facts/William_Shockley/wxlv4TcI">William Shockley</a> and <a href="/facts/Hans-Joachim_Queisser/HX7drPNb">Hans-Joachim Queisser</a> at <a href="/facts/Shockley_Semiconductor/HUKtx0v8">Shockley Semiconductor</a> in 1961, giving a maximum efficiency of 30% at 1.1 eV. The limit is one of the most fundamental to solar energy production with <a href="/facts/Photovoltaic_cell/3L814UCC">photovoltaic cells</a>, and is one of the field's most important contributions.
This first calculation used the 6000K black-body spectrum as an approximation to the solar spectrum. Subsequent calculations have used measured global solar spectra, <a href="/facts/Air_mass_(solar_energy)/grfaWYfc">AM 1.5</a>, and included a back surface mirror which increases the maximum <a href="/facts/Solar_conversion_efficiency/Au9KQeed">solar conversion efficiency</a> to 33.16% for a single-junction solar cell with a bandgap of 1.34 eV. That is, of all the power contained in sunlight (about 1000 W/m2) falling on an ideal solar cell, only 33.7% of that could ever be turned into electricity (337 W/m2). The most popular solar cell material, silicon, has a less favorable band gap of 1.1 eV, resulting in a maximum efficiency of about 32%. Modern commercial mono-crystalline solar cells produce about 24% conversion efficiency, the losses due largely to practical concerns like reflection off the front of the cell and light blockage from the thin wires on the cell surface.
The Shockley–Queisser limit only applies to conventional solar cells with a single p-n junction; solar cells with multiple layers can (and do) outperform this limit, and so can <a href="/facts/Solar_thermal/VHzn41co">solar thermal</a> and certain other solar energy systems. In the extreme limit, for a multi-junction solar cell with an infinite number of layers, the corresponding limit is 68.7% for normal sunlight, or 86.8% using concentrated sunlight (see <a href="/facts/Thermodynamic_efficiency_limit/avmge0h2">Thermodynamic efficiency limit</a> and <a href="/facts/Solar-cell_efficiency/Au9KQeed">solar-cell efficiency</a>).

Shockley–Queisser limit open-in-new

Shockley–Queisser limit