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Globally, the cumulative installed photovoltaic (PV) capacity has topped the 100-gigawatt (GW) milestone and is expected to reach 200 GW by the year 2015. More than 90% of the installed PV capacity employs bulk-silicon solar cells. Engineering problems that include thermal and optical challenges have not permitted the large-scale commercialization of concentration PV systems, lack of functional reliabilityand the concomitant lack of economic bankability-being a major barrier. For increasing the efficiency of single-junction cells beyond the Shockley-Queisser limit, several approaches based on concepts such as multiple exciton generation, carrier multiplication, hot-carrier extraction, etc., have been proposed; however, these do not seem to be commercially viable. Since both bulk-silicon and thin-film (amorphous silicon, cadmium telluride, and copper indium gallium selenide) solar cells remain as the only two commercially viable options for terrestrial PV applications, a multi-terminal multi-junction architecture appears promising for inexpensive PV electricity generation with efficiency exceeding the currently feasible 25%. The architecture exploits the present commercial silicon solar cells along with abundant and ultralow-cost materials such as Cu 2 O. With the availability of wellcontrolled manufacturing processes at the sub 2-nm length scale, it will become possible to manufacture ultra-high efficiency and ultra-low cost PV electricity generation modules based on silicon.

Rising demands of energy in emerging economies, coupled with the green house gas emissions related problems around the globe have provided a unique opportunity of exploiting the advantages offered by photovoltaic (PV) systems for green energy electricity generation. Similar to cell phones, power generated by PV systems can reach over two billion people worldwide who have no access to clean energy. Only silicon based PV devices meet the low-cost manufacturing criterion of clean energy conversion (abundance of raw material and no environmental health and safety issues). The use of larger size glass substrates and manufacturing techniques similar to the ones used by the liquid crystal display industry and the large scale manufacturing of amorphous silicon thin films based modules (~ GW per year manufacturing at a single location) can lead to installed PV system cost of $3/Wp. This will open a huge market for grid connected PV systems and related markets. With further research and development, this approach can provide $2/Wp installed PV system costs in the next few years. At this cost level, PV electricity generation is competitive with any other technology, and PV power generation can be a dominant electricity generation technology in the 21st century.

Microcracks at the device level in bulk solar cells are the current subject of substantial research by the photovoltaic (PV) industry. This review paper addresses nondestructive testing techniques that are used to detect microfacial and subfacial cracks. In this paper, we mainly focused on mono-and polycrystalline silicon PV devices and the root causes of the cracks in solar cells are described. We have categorized these cracks based on size and location in the wafer. The impact of the microcracks on electrical and mechanical performance of silicon solar cells is reviewed. For the first time, we have used the multi-attribute decision-making method to evaluate the different inspection tools that are available on the market. The decision-making tool is based on the analytical hierarchy process and our approach enables the ranking of the inspection tools for PV production stages, which have conflicting objectives and multi-attribute constraints.