Monolithic solar cells

Olson JM, Kurtz SR (1993) Current-matched high-efficiency, multijunction monolithic solar cell. US patent US... 

Small-area thin-film CdTe solar cells have been fabricated with sunlight-to-electricity conversion efficiencies near 16%, comparable to crystalline siUcon solar cells in large-scale manufacturing. Large-area monolithic integrated CdTe modules have been fabricated with efficiencies of ca 10%, comparable to crystalline siUcon modules commercially available. 

Many grades of interlayer are produced to meet specific length, width, adhesion, stiffness, surface roughness, color (93,94), and other requirements of the laminator and end use. Sheet can be suppHed with vinyl alcohol content from 15 to about 23 wt %, depending on the suppHer and appHcation. A common interlayer thickness for automobile windshields is 0.76 mm, but interlayer used for architectural or aircraft glaring appHcations, for example, may be much thinner or thicker. There are also special grades to bond rear-view mirrors to windshields (95,96) and to adhere the components of solar cells (97,98). Multilayer coextmded sheet, each component of which provides a separate property not possible in monolithic sheet, can also be made (99—101). 

Kocha, S.S., Montgomery, D., Peterson, M.W., and Turner, J.A., Photoelectrochemical decomposition of water utilizing monolithic tandem cells, Solar Energ. Mater. Solar Cells, 52,389,1998. 

High efficiency solar cells are produced from crystalline binary or multinary compounds of elements from Groups III and V, almost entirely for space applications. While a wide range of materials and methods have been employed, the monolithic tandem stack of a Ga cIni (P cell, where x 0.516, above GaAs and Ge cells is a commercially produced, indicative example.Monolithic tandem structures present several challenges. The materials used in the various junctions should have similar thermal expansion coefficients and... 

The CVD method involves a chemical reaction in a vapor phase which results in deposition of a solid on a heated surface. Various PVD processes such as ion plating, sputtering, molecular beam, evaporation, and epitaxy might be also included in CVD processes [112]. The various CVD methods are powerful processes used for the fabrications of a wide variety of thin-film materials including solar cell materials and semiconductor materials for electronic applications, as well as the manufacture of coatings, powders, fibers, and monolithic components. There are two types of CVD reactors, the differential reactor and the starved reactor, according to the value of the flow rate (F,) defined as... 

GaAs top cell rj = 17.7%) and Si bottom cell (rj = 4.4%) in a three-terminal configuration. This is the highest efficiency for the GaAs/Si monolithic tandem solar cell ever reported. 

Agrafiotis, C. C., Mavroidis, I., Konstandopoulos, A. G., Hoffschmidt, B., Stobbe, P., Romero, M., Fernandez-Quero, V. (2007). Evaluation of porous silicon carbide monolithic honeycombs as volumetric receivers/collectors of concentrated solar radiation. Solar Energy Materials and Solar Cells, 91, 474-488. doi 10.1016/j. solmat.2006.10.021. 

Designing tandem cells is complex. For example, each cell must transmit efficiently the insufficiently energetic photons so that the contacts on the backs of the upper cells are transparent to these photons and therefore caimot be made of the usual bulk metal layers. Unless the cells in a stack can be fabricated monolithically, ie, together on the same substrate, different external load circuits must be provided for each cell. The thicknesses and band gaps of individual cells in the stack must be adjusted so that the photocurrents in all cells are equal. Such an optimal adjustment is especially difficult because the power in different parts of the solar spectmm varies under ambient conditions. Despite these difficulties, there is potential for improvement in cell conversion efficiency from tandem cells. 

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