Avoiding Shading Losses in Concentrator Photovoltaics Using a Soft-Imprinted Cloaking Geometry

Abstract

Shading losses are a longstanding obstacle in photovoltaic devices, particularly in concentrator photovoltaics, where the tradeoff between shading and resistive losses limits the concentration at which the highest power conversion efficiency is achieved to values far below the capabilities of concentrator optics. Here, we demonstrate a simple and scalable fabrication method that enables large front metal coverage while keeping shading losses to a minimum. Soft-imprint lithography is used to create trenches in a transparent polymer above the metal contacts, enabling cloaking via refraction at a range of angles near normal incidence. Using optical characterization techniques, we first confirm that the metal contacts are indeed optically cloaked. We then demonstrate an increase in short-circuit current density from 29.95 to 39.12 mA/cm 2 for a Si solar cell with 25% front metal coverage before and after patterning, respectively. We investigate the angular performance of the trench pattern and further demonstrate how such a cloaking strategy could be implemented in concentrator photovoltaics to enable efficiency peaks at concentrations beyond 1000 suns.

Fluorescent Waveguide Lattices for Enhanced Light Harvesting and Solar Cell Performance

“…Coatings also offer opportunities to leverage the structure–property relations of a wide range of optical surface structures. To date, improvements in solar cell performance have been demonstrated through nanoparticles surface coatings, nanostructured diffraction and diffuse layers, nanotexturing, geometric optical structure, among many others. − …”

“…Thereby, wide-angle incident radiation is collected and transmitted across the polymer through the waveguides at sharper angles (i.e., closer to the surface normal) than otherwise dictated by Snell’s law. , The combination of multiple (two is in fact sufficient) intersecting waveguide lattices can sweep the entire practical collection window (−70 to 70°) enabling the entire angular range to be efficiently collected and directed toward the solar cell, as compared to both a uniform film and single vertically aligned lattice. Transmitting ultrawide angles of light via more direct paths toward the solar cell mitigates effects that cause losses, such as shading from the solar cell’s front contacts, ,, thereby leading to efficiency enhancements. This wide-angle light conversion would allow greater flexibility in solar installation locations and orientations and extends time of sustained energy generation, e.g., earlier into morning, later into evening, and in winter seasons (i.e., sun is closer to the horizon).…”

High aspect ratio triangular front contacts for solar cells fabricated by string‐printing

“…Sachs et al 8 also proposed patterned interconnection ribbons allowing for light trapping with total internal reflection (TIR). Tabernig et al 9 and Jahelka et al 10 designed a patterned polymer coating that refracts normally incident light away from the metal grid.…”

“…Tabernig et al 9 and Jahelka et al 10 designed a patterned polymer coating that refracts normally incident light away from the metal grid.…”

Multidirectional Polymer Waveguide Lattices for Enhanced Ultrawide-Angle Light Capture in Silicon Solar Cells

“…From an optics perspective, this can be achieved using new types of dielectric structures that elicit novel or stronger light–matter interactions via such effects as antireflection, optical mode coupling, geometric refractive optics, plasmonics, and even ray-steering. Such effects have been realized using optical material structures such as nanoparticle surface coatings, nanostructured diffractive, diffuse and scattering layers, − gratings, nanotexturing, geometric optical structures, , one-dimensional (1D) and two-dimensional (2D) lens arrays, − microscale patterning, or even more sophisticated methods such as contact cloaking, − modified front-contact shape, and alternatively designing back-contact architectures and transparent electrodes …”