Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since July 2014 are reviewed. URI: http://onlinelibrary.wiley.com/doi/10.1002/pip.2573/pdf [1] Authors: GREEN Martin A. EMERY Keith HISHIKAWA Y. WARTA W. DUNLOP Ewan Publication Year: 2015 Type: Articles in Journals

Solar Cell Efficiency Tables (Version 45)

Recent developments in photovoltaic materials have led to continual improvements in their efficiency. We review the electrical characteristics of 16 widely studied geometries of photovoltaic materials with efficiencies of 10 to 29%. Comparison of these characteristics to the fundamental limits based on the Shockley-Queisser detailed-balance model provides a basis for identifying the key limiting factors, related to efficient light management and charge carrier collection, for these materials. Prospects for practical application and large-area fabrication are discussed for each material.

/pdf/photovoltaic-materials-present-efficiencies-and-future-3yblyv6m8p.pdf

Photovoltaic materials: Present efficiencies and future challenges

Anti-reflective coatings (ARCs) have evolved into highly effective reflectance and glare reducing components for various optical and opto-electrical equipments. Extensive research in optical and biological reflectance minimization as well as the emergence of nanotechnology over the years has contributed to the enhancement of ARCs in a major way. In this study the prime objective is to give a comprehensive idea of the ARCs right from their inception, as they were originally conceptualized by the pioneers and lay down the basic concepts and strategies adopted to minimize reflectance. The different types of ARCs are also described in greater detail and the state-of-the-art fabrication techniques have been fully illustrated. The inspiration that ARCs derive from nature (‘biomimetics’) has been an area of major research and is discussed at length. The various materials that have been reportedly used in fabricating the ARCs have also been brought into sharp focus. An account of application of ARCs on solar cells and modules, contemporary research and associated challenges are presented in the end to facilitate a universal understanding of the ARCs and encourage future research.

Anti-reflective coatings: A critical, in-depth review

Porous anodic aluminum oxide: anodization and templated synthesis of functional nanostructures.

Nature routinely produces nanostructured surfaces with useful properties, such as the self-cleaning lotus leaf, the colour of the butterfly wing, the photoreceptor in brittlestar and the anti-reflection observed in the moth eye. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.

/pdf/improved-broadband-and-quasi-omnidirectional-anti-reflection-28262vbtzi.pdf

Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures

An ordered anodic porous alumina membrane has been used as a lithographic mask of SF6 fast atom beam etching to generate a 100 nm period antireflection structure on a silicon substrate. The antireflection structure consists of a deep hexagonal grating with 100 nm period and aspect ratio of 12, which is a fine two-dimensional antireflection structure. In the wavelength region from 400 to 800 nm, the reflectivity of the silicon surface decreases from around 40% to less than 1.6%. The measured results are explained well with the theoretical results calculated on the basis of rigorous coupled-wave analysis.

100 nm period silicon antireflection structures fabricated using a porous alumina membrane mask

Recently, submicron textures have been researched and applied to multicrystalline silicon solar cells in order to improve their optical performance. In this study, the antireflection and light trapping effects of submicron surface textures in crystalline Si (c-Si) solar cells were quantitatively investigated by numerical simulations based on Maxwell's equations with a simple two-dimensional (2D) surface grating model. The calculated results showed that the surface reflection loss can be effectively reduced by using submicron Si surface gratings with appropriate aspect ratios. On the other hand, higher order diffractions that are caused by surface gratings that increase optical path lengths and light absorption near the band gap wavelength are dominant only for those with periods greater than 0·5 µm. From these results, it was inferred that submicron textures are effective for light trapping as well as for antireflection in thin c-Si solar cells if appropriate dimensions are chosen. Copyright © 2007 John Wiley & Sons, Ltd.

Light trapping effect of submicron surface textures in crystalline Si solar cells

Spectral emittance and thermal stability of two-dimensional W gratings are investigated to obtain high-temperature resistive selective emitters. Numerical calculations based on rigorous coupled-wave analysis are performed to determine the structural profile of gratings with good spectral selectivity. According to the determined parameters, two-dimensional W gratings composed of rectangular microcavities with the period of 1.0 μm are fabricated on single crystalline and polycrystalline W substrates. The grating shows a strong emission peak which can be explained by the confined modes inside the cavities. The grating with 200 nm wall thickness made from a single crystalline W shows very high thermal stability over 1400 K, while the polycrystalline grating is deformed at a high temperature because of the grain growth.

High-temperature resistive surface grating for spectral control of thermal radiation

Two-dimensional surface-relief gratings with a period of 1.0–0.2μm composed of rectangular microcavities were fabricated on single crystalline W substrates to develop spectrally selective radiators for thermophotovoltaic generation. The radiators displayed strong emission in the near-infrared region where narrow-band-gap photovoltaic cells could convert photons into electricity. The enhancement of thermal emission was attributed to the microcavity effect. Power generation tests were carried out and the W gratings showed more than two times higher generation efficiency, compared to a SiC radiator. The results showed that the microstructured W radiators behave as good selective radiator, with both high efficiency and high power density.

Thermophotovoltaic generation with selective radiators based on tungsten surface gratings

A simple fabrication technique for subwavelength structured (SWS) surfaces by means of anodic porous alumina masks directly formed on Si substrates was proposed and demonstrated. By this technique, SWS surfaces were fabricated on polished single-crystalline Si and chemically etched as-cut multicrystalline Si wafers. Smoothly tapered SWS surfaces with a periodicity of 100nm and a height of 300–400nm were obtained. A low reflectivity below 1% was observed from 300to1000nm for both of the wafers, in agreement with numerical simulation. After thermal annealing at 800°C, the reflectivity of the SWS surface increased to 3%.

Hitoshi Sai

Papers

100 nm period silicon antireflection structures fabricated using a porous alumina membrane mask

Light trapping effect of submicron surface textures in crystalline Si solar cells

High-temperature resistive surface grating for spectral control of thermal radiation

Thermophotovoltaic generation with selective radiators based on tungsten surface gratings

Antireflective subwavelength structures on crystalline Si fabricated using directly formed anodic porous alumina masks