The idea of surface texturing and its utility is illustrated in Figure 6.4. It is seen that the “facet” makes two reflections necessary for backscattering of light, so that if the photons. Energy runs vertically, with zero at energy of free electron outside the device. This could be called aPIN device, with an (I) insulator […]

The experimenters have measured the I-V characteristics of the tandem device, and also of each of the separate types of junctions, and find that the open-circuit voltage of the tandem device is close to the sum of the open-circuit voltages of the separate cells. Tandem cell operating properties are clearly shown in Figure 7.11. It […]

Shown in Figure 9.5 is a schematic of a potentially low-cost tandem device that achieves direct cleavage of water into hydrogen and oxygen by visible light. This is based on two photosystems in series (tandem), with electron flows as shown in the figure. The top cell (exposed to light) is a thin film of tungsten […]

GaAs, as shown in Figure 6.3, has a suitable bandgap and direct absorption structure for solar cells. GaAlAs layers can be grown epitaxially by liquid and vapor-phase methods. Figure 6.7a shows an excellent cell using GaAlAs layers. Features of this single-junction multilayer AlGaAs/GaAs solar cell include a thin p-AlGaAs window, grown by low-temperature liquid-phase epitaxy, […]

We have spoken earlier about the optical absorption of crystalline Si as being relatively small because of the indirect bandgap. This was shown in Figure 6.3 and led to the with irradiation intensity of100 mW/cm2(about one sun). The tandem cell shows short-circuit current density 7.8 mA/cm2, open-circuit voltage 1.2 V, and power efficiency 6.5%. texturing […]

One might imagine a monolithic dual-purpose self-regulating photoelectrochemical device comprised of a multijunction tandem solar cell, electrolytic cell, and power sharing circuitry. The tandem cell structure at illumination will be efficient inherently by using several different gaps. Its series structure will give an open-circuit voltage larger than that necessary to decompose water. The excess photovoltage […]

Some crude estimates may be useful. For example, the open-circuit voltage has an upper limit Eg/e, where Eg is the semiconductor bandgap. The analysis [71] assumes a single junction and a single uniform bandgap energy. It is assumed that photons whose energy is less than the bandgap energy Eg do not contribute to the photo­current. […]

Here (Fig. 7.14) solar cells are mounted vertically on the edges of the light collecting plates, which have dissolved dyes. The upper plate collects blue photons, the dye reemits (fluoresces) and that light is sent to the cells on the edge. The fluorescence quantum efficiency of isolated dye molecules approaches unity. (Total internal reflection helps […]