sites (by volume) for the manufacturing of solar modules.29 Notable is the apparent lack of correlation between the nations in which the bulk of solar module manufacturing is sited and the nations that dominate inventive activity (as measured by USPTO patenting). (See Figure 7.2 (b).) Indeed, the United States continues to dominate global inventive activity in solar technologies despite not being the location for the greatest volume of solar module manufacturing output. (See Figure 7.2 (a).) Notably, the largest volume in the world of patents is in cutting-edge solar technologies, such as thin films, which are still produced largely in the United States. In contrast, the largest volume of manufacturing is in crystalline silicon technology modules—a technical field that no longer dominates solar technology patenting in the USPTO.

Innovation in the materials that underpin solar technologies used for energy generation may prove important in affecting the future site of manufacturing activity in this field. Numerous materials and designs can produce photovoltaic effects.30 Overall, PV technologies can be grouped into four main categories: wafer and thin film (including crystalline and amorphous silicon and cadmium telluride technologies), concentrator, excitonic (including organic polymer and dye-sensitized solar technologies), and novel, high-efficiency technologies (such as plasmonics).31 Designs based on crystalline silicon have dominated commercial PV technology, accounting for more than 80 percent of the market for commercial modules since the industry’s origin.32 Crystalline silicon may not, however, be the future. Today, thin-film solar technologies hold the second-largest proportion of the commercial market after crystalline silicon, hovering below 20 percent.33 In the 1980s, both the United States and Japan invested in thin-film amorphous silicon technologies.34 One report finds that between 1994 and 1998 the number of USPTO patents granted in amorphous silicon exceeded the number granted in crystalline silicon.35 A more recent report based on National Renewable Energy Laboratory data concluded that the cost per watt of producing thin-film PV was closing the gap with the cost of producing crystalline PV in the late 1990s and early


29 At the firm level, one U.S.-headquartered firm is among the corporate leaders (by volume) in global manufacturing of solar modules. However, the national headquarters of the corporate entities that dominate solar manufacturing may not correlate with the geographic location of those corporations’ manufacturing activities.

30 Baumann, A., Y. Bhargava, Z.X. Liu, G. Nemet, and J. Wilcox. 2004. Photovoltaic Technology Review. Berkeley, Calif.: University of California, Berkeley.

31 Curtright, A.E., M.G. Morgan, and D. Keith. 2008. Expert assessment of future photovoltaic technology. Environmental Science and Technology 42(24): 9031-9038.

32 Baumann et al. 2004. Photovoltaic Technology Review.

33PVinsights. 2011. “Suntech Lost Championship of Solar Module Shipment to First Solar in 2Q11.” Available at Accessed December 27, 2011.

34 Baumann et al. 2004. Photovoltaic Technology Review.

35 Andersson and Jacobsson. 2000. Monitoring and assessing technology choice.

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