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Photovoltaics of all kinds have excited the imagination of researchers, investors, and business people over the past four or five years as general energy prices have crept closer to those of PV. A decade ago, PV seemed merely niche-like opportunity for use in the sunniest climes and for applications that the grid did not easily reach; traffic lights, swimming pools and electric fences. Today, PV is being touted as a possible long-term supplier of up to 20 percent of the world's energy. PV has gone through booms before and there can be little doubt that it is being somewhat hyped today. But there seems no likelihood of a significant decline in the cost of traditional energy sources any time soon. This time the PV opportunity seems to have "legs."

It is no surprise then that money that is now being poured into the PV sector by businesses large and small, by investors and even by consumers and that this has prompted a surge of interest in research of new photoactive materials. Until recently, almost 100 percent of solar cells were based on crystalline silicon (c-Si), the only major exception being the thin-film amorphous silicon (a-Si) material used for "solar calculators." In the past few years, however, other thin-film materials, notably CIS/CIGS mixes and CdTe, have also started to be used and many plants around the world are now coming on stream that will manufacture solar panels using these newer materials.

The attraction of these materials is that they are (at least potentially) low-cost, low-weight and easier to manufacture than conventional PV. They have also had the advantage that PV manufacturers that use them have been able to avoid competing with the semiconductor industry for crystalline silicon. This shortage is, however, a problem that has now all but disappeared as silicon materials companies have ramped up production to meet the needs of the PV industry. The biggest challenge of thin-film PV is now getting the energy conversion ratios to a point where thin-film PV can compete directly with crystalline silicon PV in large addressable markets.