Mitigating the interference effects induced by optical cavities in superstrate thin-film silicon multi-junction solar cells
Govind Padmakumar (TU Delft - Photovoltaic Materials and Devices)
Federica Saitta (TU Delft - Photovoltaic Materials and Devices)
K. P. Sreejith (TU Delft - Photovoltaic Materials and Devices)
Paula Perez-Rodriguez (TU Delft - Photovoltaic Materials and Devices)
René A.C.M.M. van Swaaij (TU Delft - Photovoltaic Materials and Devices)
Arno H.M. Smets (TU Delft - Photovoltaic Materials and Devices)
More Info
expand_more
Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.
Abstract
A major challenge in multijunction devices is reduced light incoupling caused by interference fringes from optical microcavities. This paper reports a potential route to mitigate the interference effects with an effective front-window design. The concepts of interface scattering and grain scattering are implemented at the front side of superstrate tandem solar cells. A random texturing and periodic-hexagonal texturing approach on glass is used as interface scatterers. However, applying an interface scatterer alone is insufficient to eliminate the interference effects of optical cavities completely. Use of sputtered unintentionally doped zinc oxide (i-ZnO) or tin oxide (SnO) as grain scatterers stacked over random and periodic glass textures quenches the interference effects significantly. For a random textured glass substrate, a 1.5-μm thick i-ZnO layer could quench interference in the top cell, except for the effect of the optical cavity formed in the amorphous top cell. Hexagonal craters on glass, combined with a 0.9-μm thick i-ZnO layer, effectively mitigate fringes formed by all optical cavities in the device. This sample demonstrates the highest incoupled photon flux with 86% of photons entering the device. Use of a wide-bandgap grain scatterer, such as SnO, reduces parasitic absorption of high-energy photons while mitigating optical cavities. The design principles discussed in this work can be applied to any thin-film multijunction solar cells consisting of layers with contrasting refractive indices.
help_outline