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Assessment of the critical nature of a material for an application is a relevant notion to anticipate supply issues for an application and a territory. To establish a list of the critical materials, we have developed an approach taking into account geological scarcity, deployment logistics and societal aspects. This article aims to apply this framework to photovoltaic (PV) module interconnection. We draw the conclusion that even if concerns of critical materials are focused on Silver (Ag) scarcity (on metallization part), interconnection materials such as Tin (Sn) and Bismuth (Bi) are even more critical, mainly due to their mostly dispersive uses. This leads us to a standard module conception analysis and emphasizes the interest of improving a more modularized PV module architecture in order to improve high value recycling. An example of such a conception is given with NICE concept. Another example offering a way to optimize metallization conception toward a less consuming pattern is also described.

Color management of integrated photovoltaics must meet two criteria of performance: provide maximum conversion efficiency and allow getting the chosen colors with an appropriate brightness, more particularly when using side by side solar cells of different colors. As the cooling conditions are not necessarily optimal, we need to take into account the influence of the heat transfer and temperature. In this article, we focus on the color space and brightness achieved by varying the antireflective properties of flat silicon solar cells. We demonstrate that taking into account the thermal effects allows freely choosing the color and adapting the brightness with a small impact on the conversion efficiency, except for dark blue solar cells. This behavior is especially true when heat exchange by convection is low. Our optical simulations show that the perceived color, for single layer ARC, is not varying with the position of the observer, whatever the chosen color. The use of a double layer ARC adds flexibility to tune the wanted color since the color space is greatly increased in the green and yellow directions. Last, choosing the accurate material allows both bright colors and high conversion efficiency at the same time.

Thin HIT solar cells combine efficient surface passivation and high open circuit voltage leading to high conversion efficiencies. They require a TCO layer in order to ease carriers transfer to the top surface fingers. This Transparent Conductive Oxide layer induces parasitic absorption in the low wavelength range of the solar spectrum that limits the maximum short circuit current. In case of thin film HIT solar cells, the front surface is patterned in order to increase the effective life time of photons in the active material, and the TCO layer is often deposited with a conformal way leading to additional material on the sidewalls of the patterns. In this article, we propose an alternative scheme with a local etching of both the TCO and the front a-Si:H layers in order to reduce the parasitic absorption. We study how the local resistivity of the TCO evolves as a function of the patterns, and demonstrate how the increase of the series resistance can be compensated in order to increase the conversion efficiency.

The integration of Single-Photon Avalanche Diodes (SPADs) in CMOS Fully Depleted Silicon-On-Insulator (FD-SOI) technology under a buried oxide (BOX) layer and a silicon film containing transistors makes it possible to realize a 3D SPAD at the chip level. In our study, a nanostructurated layer created by an optimized arrangement of Shallow Trench Isolation (STI) above the photosensitive zone generates constructive interferences and consequently an increase in the light sensitivity in the frontside illumination. A simulation methodology is presented that couples electrical and optical data in order to optimize the STI trenches (size and period) and to estimate the Photon Detection Probability (PDP) gain. Then, a test chip was designed, manufactured, and characterized, demonstrating the PDP improvement due to the STI nanostructuring while maintaining a comparable Dark Count Rate (DCR). [ABSTRACT FROM AUTHOR]

Color management of integrated photovoltaics must meet two criteria of performance: provide maximum conversion efficiency and allow getting the chosen colors with an appropriate brightness, more particularly when using side by side solar cells of different colors. As the cooling conditions are not necessarily optimal, we need to take into account the influence of the heat transfer and temperature. In this article, we focus on the color space and brightness achieved by varying the antireflective properties of flat silicon solar cells. We demonstrate that taking into account the thermal effects allows freely choosing the color and adapting the brightness with a small impact on the conversion efficiency, except for dark blue solar cells. This behavior is especially true when heat exchange by convection is low. Our optical simulations show that the perceived color, for single layer ARC, is not varying with the position of the observer, whatever the chosen color. The use of a double layer ARC adds flexibility to tune the wanted color since the color space is greatly increased in the green and yellow directions. Last, choosing the accurate material allows both bright colors and high conversion efficiency at the same time. [ABSTRACT FROM AUTHOR]

Fabrication of industrial thin-film crystalline silicon solar cells remains challenging because of the high level of light trapping and surface passivation required to achieve a good conversion efficiency, while reducing the process cost. This work proposes a solution of rear side reflector supplying both passivation and light trapping, and guaranteeing compatibility with a laser process for local opening in order to use the passivated emitter and rear cell architecture. The key element is the use of substoichiometric silicon oxide deposited by plasma-enhanced chemical vapor deposition with a higher silicon concentration than the usual nearly stoichiometric oxide. This material is absorbent at usual ultraviolet laser wavelengths, and thus allows laser ablation with limited substrate heat, greatly reducing substrate damage after ablation. A layer of this oxide is incorporated into a SiOx/SiNy dielectric stack, which shows the expected qualities in term of passivation and reflectivity. [ABSTRACT FROM AUTHOR]

We report on the fabrication, integration, and simulation, both optical and optoelectrical, of two-dimensional photonic nanostructures for advanced light trapping in thin crystalline silicon (c-Si) solar cells. The photonic nanostructures are fabricated by the combination of various lithography (nanoimprint, laser interference, and hole mask colloidal) and etching (dry plasma and wet chemical) techniques. The nanopatterning possibilities thus range from periodic to random corrugations and from inverted nanopyramids to high aspect ratio profiles. Optically, the nanopatterning results in better performance than the standard pyramid texturing, showing a more robust behavior with respect to light incidence angle. Electrically, wet etching results in higher minority carrier lifetimes compared to dry etching. From the integration of the photonic nanostructures into a micron-thin c-Si solar cell certain factors limiting the efficiencies are identified. More precisely: (a) the parasitic absorption is limiting the short circuit current, (b) the conformality of thin-film coatings on the nanopatterned surface is limiting the fill factor, and (c) the material damage from dry etching is limiting the open circuit voltage. From optical simulations, the optimal pattern parameters are identified. From optoelectrical simulations, cell design considerations are discussed, suggesting to position the junction on the opposite side of the nanopattern. [ABSTRACT FROM AUTHOR]

We review recent progress in nanophotonic devices for compact optical interconnect networks. We focus on microdisk-laser-based transmitters and discuss improved design and advanced functionality including all-optical wavelength conversion and flip-flops. Next we discuss the fabrication uniformity of the passive routing circuits and their thermal tuning. Finally, we discuss the performance of a wavelength selective detector. [ABSTRACT FROM PUBLISHER]

Many applications require colored surfaces while maximizing photons to pass through with no optical losses. As the perceived color depends on the spectral content and the number of reflected photons for each wavelength, it is necessary to consider not only the chromatic content but also the brightness. As a first application example, photovoltaic modules could see their acceptance in urban situations greatly improved if their color could be controlled while maximizing the number of photons used for energy conversion. In this case, it is important to limit light brightness to avoid glare when light coming from the sun is reflected directly. As another example, a colored and semi-transparent glass layer in the infrared could efficiently protect sensors while camouflaging them, such as lidar in automotive applications. We propose a theoretical study for multicolor applications, considering 2D partially etched grating waveguide structures that behave as a perfect broadband antireflection coating while the residual layer couples light in a waveguided mode in order to reflect only a particular photon band. This strategy allows to produce a large variety of colors and the use of non-absorbing materials avoids any optical loss. The width of the resonance peak is a crucial parameter for balancing brightness in multicolor applications. In the second part, we developed a method for a fast optimization of the geometrical parameters and we applied it to obtain the three primary colors with strong geometrical constraints, so that such structures could be manufactured in a single step by nano-imprint. Finally, we propose some improvements of these structures, in particular by reducing broadband reflection to obtain more saturated colors, or to improve the angular behavior of these structures. [ABSTRACT FROM AUTHOR]