Your daily dose of Photovoltaic Technology Developments and Solar News

ABSTRACT
A vast majority of silicon solar cells are manufactured using silver paste that is screen printed onto the front side of the wafer and fired to form the front-side contact. Though this method is well established within the industry, it continues to present several areas for potential efficiency improvements. The Fraunhofer Institute has, among others, studied the potential of using electrodeposition of silver on top of the front side silver paste as a way to improve the frontside contact and increase cell efficiency.

ABSTRACT

The use of perfluorinated gases such as NF₃, CF₄ or SF₆ for PECVD (plasma enhanced chemical vapor deposition) chamber cleaning has a much higher impact on global warming than does the use of onsite-generated F₂. This holds true even when supposing that in the future much more effort is paid for the correct abatement and a leak-free supply and take-back chain. This paper will discuss the steps available to the PV industry for control and reduction of carbon emissions in the chamber cleaning process.

By Guy Beaucarne, Patrick Choulat, B.T. Chan, Harold Dekkers, Joachim John & Jef Poortmans, IMEC, Belgium -

ABSTRACT -
Si etch processes are vital steps in Si solar cell manufacturing. They are used for saw damage removal, surface texturing and parasitic junction removal. The next generation of Si solar cells, featuring thinner wafers and passivated rear surfaces, will pose more stringent demands on those steps. Surface decoupling (achieving different surface treatments on the front and the rear) has to be achieved while minimizing Si consumption. Plasma texturing is an emerging technique that appears very promising in that respect, as efficiencies as high as 17.4 % have been achieved on screenprinted multicrystalline Si solar cells incorporating this process.

By Dorit Linaschke, Mattias Leistner, Gerrit Mäder, Wulf Grählert, Ines Dani & Stefan Kaskel, Fraunhofer IWS,Dresden, Germany

ABSTRACT

The etching technology currently used in the solar industry is mostly based on wet chemical processing. Plasmaenhanced dry chemical etching at atmospheric pressure is an alternative to the existing technology, especially when combined with similar process technologies, for example plasma-enhanced deposition techniques at atmospheric pressure, to provide a continuous in-line processing of crystalline silicon solar cells. This paper presents the use of plasma chemical etching using Fourier Transform infrared (FT-IR) spectroscopy to monitor different silicon wafer processing steps as an alternative to the widely used wet chemical processing approach.

By Michael Kostwald, Turner & Townsend GmbH, Germany; Hans Mahrenholtz, Linde Gas, Linde AG, Germany; &
Anish Tolia, Linde Electronics, U.S.A.

ABSTRACT
Thin-film solar cell manufacturing is poised to make a giant leap in scale with the birth of the gigawatt fab. Commercial thin-film plants are typically sized based on the capacity of the production line from the chosen equipment supplier. In most cases, initial investments have been for a single line, typically with an output capacity of no more than 60MWp. This period of initial development has allowed the industry to prove the robustness of the technology and capabilities of the equipment, as well as to understand the significance for the cost-per-watt of key cost drivers such as materials reduction, cell efficiency increases, and productivity. While large-scale manufacturing will positively impact costs, it presents a unique set of challenges for equipment and material suppliers, as well as the engineering and contracting
companies tasked with designing, building, equipping and running a facility on this scale. In this paper, we present the insights of two specialty companies in the solar industry. Turner and Townsend, a design and project management consultancy, and Linde, glass manufacturer and gas and chemical company – share their views of the challenges of the gigawatt fab in three dedicated sections.

By Hanne Degans, Izabela Kuzma, Guy Beaucarne & J. Poortmans, IMEC, Belgium

ABSTRACT
Thin-film silicon solar cells are a potentially low-cost alternative to solar cells based on bulk silicon that are commonly used in the industry at the present time. However, a major drawback of the current epitaxial semi-industrial screenprinted cells is that they only achieve an efficiency of about 11-12%. By upgrading their efficiency, this kind of solar cell would become more attractive to the photovoltaic industry. The optimization of the front surface texture by dry texturing based on a fluorine plasma and the introduction of an intermediate porous silicon reflector at the epi/ubstrate interface (multiple Bragg reflector) has proven to result in an efficiency boost up to about 14%.

By Sylvère Leu, Conergy AG, Frankfurt, Germany

ABSTRACT
Each year, the photovoltaic market has been achieving a two-digit growth rate. The resulting economy-of-scale effects are not enough to achieve grid parity on their own. In order to reduce the production costs to grid parity level, new concepts and ideas must be realised as the basis for a photovoltaic factory. There are four main requirements that must be fulfilled in order to adhere to this cost reduction strategy: a highly integrated factory; automated and stable processes; a production control system (PCS) that provides the statistic data in order to continually optimise the processes; and an optimally-sized aligned production capacity.

By Sarah Kurtz, National Renewable Energy Laboratory (NREL), Golden, Colorado, USA

ABSTRACT
Today’s PV industry is growing at a rapid rate, but the industry would grow even faster if costs could be reduced for both the final products and the capital investment required for scale-up. One strategy for reducing module costs to reduce the amount of semiconductor material needed (the cost of the silicon solar cells typically comprises more than half of the module cost).

By Bettina Weiss, PV Group (North America), SEMI, USA

ABSTRACT
Many readers will equate SEMI with the SEMICON trade shows around the world, business and technical conferences, EHS and advocacy initiatives and, most of all, industry standards. Currently, SEMI has close to 2,000 member companies, about 20% of which are active in the photovoltaic sector. These companies form a community called PV Group. The mission of the PV Group is to serve the photovoltaic market with events, standards and services. Working with other industry groups throughout the world, SEMI is dedicated to advancing the growth and profitability of its members, and to achieve overall cost reduction to enable PV energy adoption worldwide. We listen closely to our constituents’ needs and are committed to developing unique approaches to unique problems. Connecting markets and industries that benefit from dialogue has been our mission for 38 years. Between former semiconductor professionals moving into PV, pure PV manufacturers and a startling number of start-ups, there is fertile ground for collective discussions in all regions of the world that are necessary to propel us forward.

By Paula Mints, Navigant Consulting, Inc., Palo Alto, California, USA

ABSTRACT
The photovoltaic industry was once, and for quite some time, the unappreciated renewable technology. Perceived as too expensive without subsidies to reduce the price of ownership, and sometimes as an energy choice primarily for environmental zealots, the industry has continued, nonetheless, to grow at a compound annual rate of 34% over the past 30 years. Growth at this rate would be envied by any industry, and certainly deserves recognition, particularly as it has come with significant problems and has been extremely difficult to achieve. Now, with worldwide consensus on global warming along with sufficient evidence that fossil fuels are rapidly depleting, solar electricity is finally earning some respect – but the industry still has perception problems to solve.