The two-terminal series-connected configuration provides the fewest possibilities for interconnection of the devices. This configuration requires that the subcells be of the same polarity and that the photocurrents of the subcells be closely matched, since in this series connection the subcell with the least photocurrent limits the current generated by the entire device. This current-matching […]

In contrast, in the three-terminal configuration the subcells are not electrically isolated; the bottom of each cell is electrically connected to the top of the cell beneath it. The fabrication of a monolithic three-terminal device is relatively straightforward, although more complex than the fabrication of a two-terminal device. The semiconductor structure must be designed to […]

8.1.3 Four-terminal There are several ways to connect power leads to the junctions comprising a multijunction stack. These configurations, which provide for varying degrees of electrical isolation of the subcells, are illustrated in Figure 8.4c for a two-subcell stack. In the four-terminal configuration, each subcell has its own two terminals and is electrically isolated from […]

The multijunction approach requires that an incident photon with a given energy be directed onto the correct subcell. Perhaps the conceptually simplest approach would be to use an optically dispersive element such as a prism to spatially distribute photons with different energies to different locations, where the appropriate cells would be placed to collect these […]

Henry has calculated the limiting terrestrial one-sun efficiencies for conversion with 1, 2, 3, and 36 bandgaps; the respective efficiencies are 37, 50, 56, and 72% [16]. The improvement in efficiency from one to two bandgaps is considerable, but the returns diminish as more bandgaps are added. This is fortunate since the practicality of a […]

8.1.2 Wavelength Dependence of Photon Conversion Efficiency As a prelude to the detailed examination of the design and performance of multijunction cells, it is useful to review briefly the fundamental factors that limit the efficiency of single-junction cells. Consider an ideal single-junction cell with characteristic bandgap Eg. A photon incident on this cell with photon […]

The PV industry currently services a wide range of terrestrial applications, from power for small consumer products to larger grid-connected systems. III-V solar cells are currently too expensive for most one-sun applications. While satellites represent an example of an application for which the extra cost is acceptable, for bulk electricity generation, a concentration of 400 […]

8.1.1 Space Solar Cells The higher efficiencies and radiation resistance of III-V cells have made them attractive as replacements for silicon cells on many satellites and space vehicles. Over the years, III-V mul­tijunction cells have largely replaced silicon cells on new satellite launches. The GaInP/GaAs/Ge cells are integrated into modules very much like single-junction solar […]