Solar photovoltaic electricity: Current status and future prospects

Black silicon (BSi) represents a very active research area in renewable energy materials. The rise of BSi as a focus of study for its fundamental properties and potentially lucrative practical applications is shown by several recent results ranging from solar cells and light-emitting devices to antibacterial coatings and gas-sensors. In this paper, the common BSi fabrication techniques are first reviewed, including electrochemical HF etching, stain etching, metal-assisted chemical etching, reactive ion etching, laser irradiation and the molten salt Fray-Farthing-Chen-Cambridge (FFC-Cambridge) process. The utilization of BSi as an anti-reflection coating in solar cells is then critically examined and appraised, based upon strategies towards higher efficiency renewable solar energy modules. Methods of incorporating BSi in advanced solar cell architectures and the production of ultra-thin and flexible BSi wafers are also surveyed. Particular attention is given to routes leading to passivated BSi surfaces, which are essential for improving the electrical properties of any devices incorporating BSi, with a special focus on atomic layer deposition of Al2O3. Finally, three potential research directions worth exploring for practical solar cell applications are highlighted, namely, encapsulation effects, the development of micro-nano dual-scale BSi, and the incorporation of BSi into thin solar cells. It is intended that this paper will serve as a useful introduction to this novel material and its properties, and provide a general overview of recent progress in research currently being undertaken for renewable energy applications.

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Black silicon: fabrication methods, properties and solar energy applications

PROBLEM TO BE SOLVED: To provide a solar cell that can reduce a manufacturing cost therefor, and that can improve the efficiency.SOLUTION: A solar cell according to one feature of the present invention comprises: a substrate (110) of a first conductive type; an emitter layer (120) of a second conductive type opposite the first conductive type, the emitter layer configured to form a p-n junction along with the substrate; a plurality of first electrodes connected to the emitter layer, each of the plurality of first electrodes (141) having a multi-layered structure; at least one first current collector (142) that is connected to the plurality of first electrodes and has a single-layered structure; and a second electrode (151) connected to the substrate. This improves the efficiency in manufacturing a solar cell, and reduces the manufacturing cost.

Solar cell and method for manufacturing the same

A method and apparatus for etching photomasks is provided herein. In one embodiment, the apparatus comprises a process chamber having a support pedestal adapted for receiving a photomask. An ion-neutral shield is disposed above the pedestal and a deflector plate assembly is provided above the ion-neutral shield. The deflector plate assembly defines a gas flow direction for process gases towards the ion-neutral shield, while the ion-neutral shield is used to establish a desired distribution of ion and neutral species in a plasma for etching the photomask.

Method and apparatus for photomask plasma etching

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

Surface texturing of large area multicrystalline silicon solar cells using reactive ion etching method

A surface electrode (5) is installed on the light receiving surface of a solar cell element, the surface electrode (5) comprises three bus bar electrodes (5a) for retrieving light-produced current produced at the solar cell element to the outside and collecting finger electrodes (5b) connected to these bus bar electrodes (5a), and the bus bar electrodes (5a) are 0.5 mm through 2 mm in width and the finger electrodes (5b) are 0.05 mm through 0.1 mm in width. A high-efficient solar cell module can be obtained with substantially lowered resistance by increasing the number of bus bar electrodes (5a) and thereby decreasing the lengths of the finger electrodes (5b).

Solar Cell Module and Photovoltaic Power Generator Using This

A surface of a multicrystalline silicon substrate is etched with an alkaline aqueous solution in a condition so that a surface area-to-planar surface area ratio R is smaller than 1.1. A multiplicity of fine textures are formed over the irregularities by dry etching. This allows fine textures to be formed uniformly, and a solar cell with high efficiency can thus be produced.

Multicrystalline silicon substrate and process for roughening surface thereof

We have developed a new surface texturing technique using a reactive ion etching (RIE) method for multicrystalline silicon (mc-Si) solar cells, which is expected to form a low reflectance surface on grains of various crystalline orientations This surface texture has a cone shape, and aspect ratio and size of which can be easily controlled We have optimized surface shape and emitter sheet resistance The optimum emitter sheet resistance for RIE textured cell is higher than that for the usual cell The high aspect ratio of the cone shape makes surface reflectance low, but the cell efficiency is not so good There is an optimum aspect ratio because the emitter of cell with high aspect ratio surface has large saturation current and cell performance is decreased with aspect ratio We have fabricated over 17% efficient large area (225 cm/sup 2/) mc-Si solar cell using this surface texturing technique and passivation schemes which is based on the silicon nitride film deposited by the plasma CVD method and hydrogen annealing at a high temperature

Surface texturing using reactive ion etching for multicrystalline silicon solar cells

PROBLEM TO BE SOLVED: To dissolve complicated works of long time in a manufacturing process, and enable uniformly to etch the whole surface of a semiconductor wafer. SOLUTION: In a method of manufacturing a solar cell element, a semiconductor substrate 1 is carried in a dry etching apparatus, a very small uneven part 1b is formed on the front side of the semiconductor substrate, a PN junction part is formed on the front side of the semiconductor substrate, and electrodes 5, 6 are formed on the front side and the back side of the semiconductor substrate. After the semiconductor substrate 1 is carried in the dry etching apparatus, gas for forming a mask and etching gas are simultaneously introduced in the dry etching apparatus, and the very small uneven part 1b is formed on the semiconductor substrate 1. The shape of the uneven part 1b is effectively optimized by introducing gas for flattening a shape simultaneously or continuously after the very small uneven part 1b is formed. COPYRIGHT: (C)1997,JPO

Yosuke Inomata

Papers

Surface texturing of large area multicrystalline silicon solar cells using reactive ion etching method

Solar Cell Module and Photovoltaic Power Generator Using This

Multicrystalline silicon substrate and process for roughening surface thereof

Surface texturing using reactive ion etching for multicrystalline silicon solar cells

Manufacture of solar cell element