Improving the voltage of solar cells using photon management

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Title: Improving the voltage of solar cells using photon management This work focuses on the study of new approaches to enhance the efficiency of solar cells through novel approaches to manage photon absorption. The efficiency of solar cells is determined by both the photocurrent and the operating voltage. Currently, photocurrents in many leading cell technologies are approaching their upper limit, leaving little room for improvement. On the other hand, operating voltages are still lagging behind their predicted limit. Traditionally, the voltage could only be enhanced by improving the quality of solar cell materials, which tends to increase the cost significantly. In this effort new approaches will be developed based on optical designs to improve the operating voltage. Theoretical and experimental studies aim to establish new mechanisms and design principles for voltage enhancement based on photonic engineering. By investigating strategies for increasing cell voltage, the PI anticipates improved understanding of fundamental processes that will lead to higher efficiency of solar systems. There is a strong educational plan to involve students with the research effort and to collaborate with an industrial partner. The project will train undergraduate and graduate students in clean energy technologies which will have a profound impact on society. The proposed work focuses on new approaches to enhance the operating voltage of solar cells. Several new mechanisms using photon management in semiconductor nanostructures will be investigated. The proposed photon management seeks to address issues beyond anti-reflection and light trapping. Photonics can improve the voltage through the Purcell effect where radiative recombination rates are enhanced or suppressed by engineering the optical density of states. Such effects become more important as solar cells reach high efficiencies, particularly for direct bandgap semiconductors. Near-field emission will be theoretically investigated in various nanostructures to reduce the loss of voltage in practical solar cells. The project combines detailed balance analysis and nanophotonic simulations. In particular, cell architectures will be investigated to achieve efficiency beyond the Shockley-Queisser limit.