Nanotechnology Pathways to Next-Generation Photovoltaics

Abstract

In this book chapter, an overview is given of the latest advances and central challenges in photovoltaics research, and the role of nanotechnology in improving performance. Over the long term, nanotechnology is expected to enable improvements throughout the energy sector, but the most striking near- to midterm opportunities may be in lower-cost, higher-efficiency conversion of sunlight to electric power. Nanostructures in solar cells have multiple approaches by which they can improve photovoltaic performance: (1) new physical approaches in order to reach thermodynamic limits, (2) allow solar cells to more closely approximate their material-dependent thermodynamic limits, and (3) provide new routes for low-cost fabrication by self-assembly or design of new materials. We focus primarily on the first two approaches which have the goal of increasing efficiency. The limits of solar cell efficiencies are discussed, and several different approaches are described that circumvent long-held physical assumptions and lead beyond first- and second-generation solar cell technologies. The role of nanotechnology in specific cell technologies is reviewed, including its role in improving light-trapping and the light collection properties of solar cells, as well as dye-sensitized solar cells and perovskite solar cells, and recent advances in nanowire solar cells. Special emphasis is given on novel nanostructure-based devices based on advanced concepts such as hot-carrier cells, and multiexciton generation, which have the theoretical basis to realize high-efficiency energy conversion.