Nanostructured Photovoltaics

In this review, we begin by discussing the need for harnessing renewable energy resources in the context of global energy demands. A summary of first- and second-generation solar cells, their efficiency and grid parity is provided, followed by the need to reduce material and installation costs, and achieve higher efficiencies beyond the Shockley-Queisser limit imposed on single junction cells. We also discuss the specific advantages offered by nanomaterials in enhanced energy harvesting, what design platforms comprise nanostructured photovoltaics, and list the prominent categories of nanomaterials used in the design of third generation solar cells. We review the significant nanostructured photovoltaic platforms that have encouraging power conversion efficiencies, have the potential for long term stability (both structural and functional) and have received attention in the field. In addition to their operational principle, we highlight both their advantages and shortcomings, along with insights into possible improvements. We include alternate routes to improving power conversion efficiency, not by tuning material properties to match the solar spectrum but using additives and/or structural modifications to allow more efficient harvesting of sunlight, either by reducing losses or by altering the spectral properties. The properties of nanomaterials that make them well-suited as active materials in photovoltaic devices (broadband absorption, high quantum yield, etc.) also make them ideal candidates for luminescent solar concentrators (LSCs). These devices also harvest solar energy, but instead of directly allowing charge generation, they act as downconverters for other photovoltaic cells. We review dye, thin film, and quantum dot based LSCs that have garnered a lot of attention in recent years as these devices face a resurgence given the advances in materials science and engineering which have led to novel quantum dots and hybrid semiconductors. The review ends with where the future of nanostructured photovoltaics is headed, what device designs and materials development are needed to achieve efficiencies beyond the Shockley-Queisser limits and fulfil the goal of the 3rd and 4th generation photovoltaics.