{"Page URL":"https://www.appropedia.org/Multi-junction_solar_cells","Page description":"Multi-junction (MJ) use multiple semiconductor[[Wikipedia:semiconductor|W]] layers (subcells) to produce electricity at high operating efficiencies. Each layer has a unique band gap[[Wikipedia:band gap|W]] designed to efficiently absorb a specific segment of the solar spectrum[[Wikipedia:solar spectrum|W]]. This has two important advantages over single-junction (SJ) devices: a wider range of absorption of incident photons[[Wikipedia:photons|W]] as well as a more effective energy extraction from these photons. The lowest band gap of a MJ cell will be lower than that of a typical SJ band gap. Therefore, the MJ cell can absorb extra photons that possess less energy than the SJ band gap but greater than its own lowest band gap. The MJ cell will absorb the same photons more efficiently since having band gaps closer to the photon energy will reduce thermalization losses. For example, a SJ band gap of 1 eV could extract only 1 eV from a 3 eV photon with 2 eV wasted via thermal decay. On the other hand, a MJ cell with a top band gap of 2 eV will extract twice the energy from the same photon. Figure 1 illustrates the difference in energy absorption between a triple MJ cell and a SJ cell. The colored areas show the amount of that can be extracted by each cell. Table 1 gives the optimum band gaps and corresponding efficiencies for MJ cells. The table illustrates how additional junctions raise maximum . However, adding junctions also increases the device's complexity and cost. It must be noted that the use of concentrators gives an additional boost to potential efficiency.","Page image":"File:MJ.Efficiencies.JPG","Page language":"en","Page license":"CC-BY-SA-3.0","Page title":"Multi-junction solar cells","Page views":"3380","Page year":"Friday, 01-Jan-10 00:00:00 UTC","Modification date":"Friday, 28-Nov-25 13:27:47 UTC"}