Spectrophotometric analysis of stochastic hybrid black silicon nanostructures for crystalline silicon photovoltaic cells


Author(s): J. Tyson

Publisher: University of Southampton

Publication Date: n/a

Abstract:

Black silicon nanotextures offer exceptionally low levels of reflectance and are of interest to the field of solar photovoltaics. The nanowires that form this texture create a graded refractive index, allowing light to be absorbed with high efficiency. Explored here is the application of these nanotextures on top of conventional microscale pyra- mids, combining the advantages forwarded by the latter, predominantly being a second chance for absorption, and the former, being light steering. These structures are known as hybrid black silicon. Variations on the wet chemical etch parameters are explored and related to topological features, which can, in–turn, be related to front surface reflectance. The hybrid black silicon textures created are shown to exhibit reflectance as low as 0.7%.

An advanced hemispherical reflectometry system is reported, designed for measuring the optical characteristics of a variety of samples resolved against wavelength, angle of incidence, and polarisation. Variable angle reflectance data enables a new perspective on the interaction between electromagnetic waves and nanostructures, which do not interact with light in the same way as their microscale counterparts. The versatility of this data is demonstrated for photovoltaics when combined with geographic spectral irradiance data. Solar cell optical performance, when structured with the textures measured in the reflectometer, is successfully predicted should that cell be placed in Southampton, UK. This mathematical formulation is capable, alongside the appropriate angle–resolved reflectance data, of approximating the optical performance of a given sample when situated almost anywhere in the world.

Supporting the reflectance data gathered through this work is a black silicon nanowire model, pseudorandomised using custom–made algorithms against a set of desired surface features. The model uniquely generates complex surface topologies that meet the requirements of electromagnetic wave optics simulations. The model reported showcases an accuracy within the ±2% relative error against measured reflectance, and offers a new, fast, and accurate way of simulating nanostructures without the need to manufacture them in bulk.

The full text for this publication is currently unavailable. It is scheduled to be released in the coming weeks.


Characterising the broadband, wide–angle reflectance properties of black silicon surfaces for photovoltaic applications


Author(s): J. Tyson, T. Scheul, T. Rahman, and S. Boden

Publisher: Optica Publishing Group

Publication Date: August 2023

Abstract:

Black silicon nanotextures offer significant optical performance improvements when applied to crystalline silicon solar cells. Coupled with conventional pyramidal textures, to create so–called hybrid black silicon, these benefits are shown to be further enhanced. Presented here is a comprehensive analysis of different variations of this texture, coupled with typical anti–reflectance schemes such as coated pyramids, with a view to the significance of this on subsequent, real–world, solar energy generation. The study uses an angle–resolved spectrophometry system to characterise and compare the optical properties of these surface textures in terms of reflectance versus wavelength and incident angle, with and without encapsulant layers. This analysis, coupled with time-resolved, location specific irradiance data, leads to a new figure-of-merit, the weighted reflectivity, with which to compare surface textures for use in solar cells. Weighted reflectivity for an encapsulated solar cell surface, averaged over a year, for a Southampton, UK, location is calculated to be 7.6% for hybrid black silicon, compared to 10.6% for traditional random pyramids with a thin film anti–reflective coating.

This publication is open access and is available here.


Analysing the optical performance of hybrid black silicon surface textures under variable angle illumination


Author(s): J. Tyson, T. Rahman, and S. Boden

Publisher: SuperSolar Group

Publication Date: September 2022

Abstract:

We showcase the optical performance of our hybrid black silicon (hb-Si) nanotextures, as measured with our bespoke angle-resolved spectrophotometer (ARS) and delve into a real-world analysis of its day-to-day performance. Using our novel reflectance measuring technique we can combine theoretical solar irradiance with measured surface reflectance, resolved against wavelength, angle, and polarisation simultaneously, to get a unique insight into how solar cells would perform, optically, when placed anywhere in the world. Here, we take several locations, including Manchester in the U.K., Narangba in Australia, and Reykjavík in Iceland, and perform such a theoretical analysis for each at various points throughout the year, forming a comparison study with a traditional pyramidal textured sample under the same conditions.

This publication is currently not available to download. This is typically due to copyright restrictions.


Developing outdoor testing equipment for insolation measurement of bifacial solar tracking systems for evaluation purposes


Author(s): Y. Musleh, J. Tyson, C. Cao, S. Boden, and T. Rahman

Publisher: The UK Solar Energy Society

Publication Date: April 2022

Abstract:

ABSTRACT HERE

This publication is currently not available to download. This is typically due to copyright restrictions.


Hybrid black silicon nanotextures and their implications on the time-varying performance of solar photovoltaic technologies in the real world


Author(s): J. Tyson, T. Rahman, S. Boden

Publisher: The UK Solar Energy Society

Publication Date: April 2022

Abstract:

ABSTRACT HERE

This publication is currently not available to download. This is typically due to copyright restrictions.


A ground-breaking new system to accurately measure light reflection from a shifting source


Author(s): J. Tyson, T. Rahman, and S. Boden

Publisher: Future Worlds

Publication Date: March 2022

Abstract:

In developing a solution to tackle the lost energy potential of reflection of light from the surface of solar cells – using nanoscale textured ‘black’ silicon - a new, ground-breaking innovation emerged. The Variable Angle Reflectometer (VAR) is designed to measure the reflectance of a given surface, resolved not only against wavelength, but also against incident angle.

This publication is open access and is available here.


Angle-resolved spectrophotometry for the optical characterisation of material surfaces


Author(s): J. Tyson, T. Rahman, and S. Boden

Publisher: Institute of Electrical and Electronics Engineers

Publication Date: January 2022

Abstract:

Surface reflectance is a practical metric of the optical performance of a material. Applications, such as glass manufacturing, light sensing, satellite reflectors, and photovoltaics, depend on their reflectance properties and generalized optical performance. Reflectance measurements are rarely reported comprehensively, with only a single angle of incidence common in most datasets. Here, we present a new spectrophotometry system capable of performing angle-, wavelength-, and polarization-resolved reflectance measurements on various surfaces. Data from such a system yields significant information regarding the everyday, real-world performance of said materials. We perform exemplar studies by characterizing several standard thin-film antireflectance coatings and comparing the results to their known theoretical optical response. We also present results from measurements on an optical insulating material as well as a selection of wall paints to showcase the versatility of the technique. We highlight the parallels between measurement and theory, while analyzing the realistic implications of the measurements on their respective material’s practical performance under real-world conditions.

This publication is open access and is available here.