Nanostructured Inorganic Solar Cells

Abstract

Abstract. Recent progress in the development of nanostructured inorganic solar cells is reviewed. Nanostructuring of inorganic solar cells offers the possibility of reducing the cost of photovoltaics by allowing smaller amounts of lowergrade photovoltaic semiconductors to be used. Various fabrication methods used to nanostructure traditional photovoltaic semiconductors are detailed and the performance of resulting devices is discussed. The synthesis of solar cells by solution-based methods using less traditional, abundant materials is identified as a promising route to widescale photovoltaic electricity generation, and nanostructured solar cell geometries are highlighted as essential in this approach. Templating and self-assembling methods used to produce appropriate low-cost nanostructures from solutions are detailed, and the performance of preliminary ultra-lowcost cells made with these structures is reviewed.Keywords. Photovoltaic, nanostructured, inorganic. PACS® (2010). 81.07.-b, 88.40.hj, 88.40.hm. Why Nanostructure? An Introduction to the TopicIt has been predicted that the world's annual energy consumption will grow from its 2009 level of around 15 terawatt-years (TWyr) to as much as 30 TWyr by 2050 [1,2]. With more than 100,000 TW of solar power striking the earth at anytime, photovoltaic technology has long been regarded as an integral part of the solution to the world's energy problems [2,3]. Yet, the high cost of traditional photovoltaic technologies has prevented them from displacing a meaningful fraction of the electricity we derive from fossil fuel sources. Fortunately, the prospects for inexpensive photovoltaic electricity generation are improving. In recent years much research has focused on reducing the price, or cost per watt, of photovoltaic cells. In particular, the emergence of fabrication and characterization techniques on the nanometer scale (nanotechnology) has enabled new strategies to harness the sun's power in a cost-effective way. In this review, the manner in which nanotechnology is being used to improve the cost-performance balance of photovoltaic cells composed of inorganic semiconductors will be discussed. The basics of solar cell operation will be briefly explained and traditional solar cells composed of expensive, highly-crystalline inorganic semiconductors will be summarized. Next, we will explain how controlling the morphology of the semiconductors on the scale of hundreds of nanometres or less can improve the collection of electricity-generating charges from the cells, reducing their stringent materials requirements and permitting cheaper fabrication. Various techniques for fabricating nanostructures of traditional photovoltaic semiconductors will be detailed and the performance of state of the art nanostructured inorganic solar cells will be reported. A discussion will follow, in which the availability of traditional photovoltaic semiconductors and the methods for producing relevant nanostructures will be evaluated in the context of whether truly inexpensive solar cells can...

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