Many methods to improve the solar cell’s efficiency beyond current generation of bulk and thin film of photovoltaic (PV) devices have been reported during the last five decades. Concepts such as multiple exciton generations (MEG), carrier multiplication (CM), hot carrier extraction, and intermediate band solar cells have fundamental flaws, and there is no experimental evidence of fabricating practical higher efficiency solar cells based on the proposed concepts. To take advantages of quantum features of nanostructures for higher performance PV devices, self-assembly-based bottom-up processing techniques are not suitable for manufacturing due to inherent problems of variability, defects, reliability, and yield. For processing nanostructures, new techniques need to be invented with the features of critical dimensional control, structural homogeneity, and lower cost of ownership as compared to the processing tools used in current generations of bulk and thin-film solar cells. 1. Introduction Starting with providing power to first communication satellite, Telstar, in 1962, photovoltaic (PV) systems have evolved to a market size of about 16 GW in 2010. Current commercial PV market is based on bulk solar cells (Si and III-V compound semiconductors) and thin-film solar cells based on a-Si, CdTe, and CuInGaSe2, while the devices are based on p-n homo- and heterojunctions and tandem junction solar cells. In case of III-V compound semiconductor-based concentration solar cells, one sun efficiency of 35.8% has been achieved [1]. Being an active area of research, new materials and structures are constantly being investigated in the hope of getting efficiencies higher than the typical bulk silicon solar cell efficiency of about 20%. Solar cells, which can be possibly made from engineered materials and nanostructures, are often called “third-generation PV cells” [2], with the materials themselves being referred to as “next generation materials,” “smart materials,” or “intelligent materials.” In reality, despite the semantics and the buzz, there has been no improvement in the efficiency of a solar cell using the so called “smart materials.” Of course, with better engineering, conventional bulk and thin-film solar cells have become more reliable, their cost has decreased over the years, and their efficiencies have also increased by a small percentage. However, this increase in efficiency cannot be attributed to any nanostructured smart material. This raises the interesting first question—during the last 10 years, why has there been no significant increase in the
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