Photovoltaics International Papers

Although the entire solar manufacturing industry, from raw materials to finished modules, has enjoyed strong double-digit growth rates over the past several years, few sectors have soared like the amorphous-silicon thin-film photovoltaic equipment space. Much of this prodigious multibillion-dollar booking activity can be attributed to the acceptance of the turnkey production packages offered by the likes of Applied Materials, Oerlikon and Ulvac. These suppliers’ plug-and-play, standard toolset solutions are attractive to companies seeking to get into the TFPV module business on a fast track and then scale up their capacities in multimegawatt chunks to achieve grid-competitive cost-per-manufactured-watt metrics.

With the thin-film silicon industry facing the problems of high-quality material deposition at high rates and narrowing deposition process windows, the “no-drift regime” is an important part of this development. In the case of the plasma-enhanced chemical vapor deposition (PECVD) of thin silicon films, the inconstancy of the concentration of silicon-containing particles (SCP) in the plasma leads to changes in deposition conditions, causing a deterioration of film properties, and, therefore, decreasing the performance of the solar cells. During the last few decades, evidence about the process instabilities has been accumulated in different laboratories. In this study, Fourier transform infrared absorption spectroscopy (FTIR), optical emission spectroscopy (OES), self-bias voltage and plasma impedance controls were applied as in-situ process diagnostics during the deposition of amorphous and microcrystalline silicon thin-films. Results of the study were then discussed.

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.

The Semiconductor Equipment and Materials International (SEMI) International Standards Program has a proven track record of more than 35 years of facilitating standards for high-tech industries, and aims to apply its experience to the emerging PV industry. Unlike other pre-established industries, where standard activities are mainly initiated by mature companies with clear requirements to standards, the PV industry, with its huge number of newly founded companies, is currently focused on ramping up their production lines and stabilizing their production processes. By structuring and utilizing standards requirements, it is possible to focus recourses to the most valuable standards in this critical phase of the fast-growing PV industry. SEMI intends to achieve these goals by proving recommendations for new standards activities, linking experts together to accomplish the deliverables, and speed up the process of standards deployment.

Inline processing, one of the fastest-growing production processes for crystalline silicon solar cells, uses continuously operated belt furnaces to achieve higher overall throughput compared with traditional batch processing. A second, major advantage of inline processing is improved manufacturing yields through reduced breakage of today’s thinner, increasingly delicate wafers. This is accomplished by eliminating several handling steps unique to batch processing techniques. This paper describes the influence of ECN-Clean, as developed by Mallinckrodt Baker and ECN in 2006, whose application increases the efficiency of solar cells produced using inline processing by approximately 0.3 percent absolute, compared with standard inline processing.

Investments in large photovoltaic factories can lead to high capital expenditure. To achieve a fast return on investment, it is essential to ensure a high utilization of process equipment. Optimization of photovoltaic factory performance requires a fundamental understanding of the processes as well as of the material flow and manufacturing equipment. Fraunhofer IPA has developed an approach to gather and analyze the factory data in order to detect and understand the logistic influencing factors. With this factory data, the performance of material flow systems and production equipments can be evaluated, leading to detection and elimination of inefficiencies in the manufacturing lines. The methods of acquiring and analyzing factory performance data as outlined in this article mainly focus on thin-film manufacturing lines, but are also applicable to crystalline technologies.

A new wafer technology, named CDS (Crystallization on Dipped Substrate), is under development and has been found to be effective in the reduction of wafer cost and silicon feedstock. CDS technology was applied to 156mm x 156mm-sized wafers, obtained via the throughput of 1825cm2/min, and the resulting cell efficiency of 14.8% was confirmed. This paper outlines the principle behind the technology and outlines the procedure.

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 [1] 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 front-side contact and increase cell efficiency. These results have shown cell efficiency increases of up to 0.4% absolute. This type of improvement has captured the interest of many manufacturers, but there has been a hesitancy to adopt electrodeposition as there is uncertainty as to what they can expect on their cells. Since efficiency gains are dependent upon many factors that can be unique to an individual cell, this paper provides a much-needed exploration of the potential effects of electrodeposition of silver in a way that isolates its effects from that of other factors.

Crystalline wafer and thin-film photovoltaics manufacturing have experienced dramatic expansion in recent years, but future growth requires increasingly effective strategies to reduce costs and increase the competitiveness of PV power. Reducing PV manufacturing costs has been a prime focus of the industry. In the current climate, cost reduction is especially critical given the industry shakeout that many analysts are forecasting. Now more than ever, it is important to bring manufacturing capacity online quickly and cost effectively. The vast majority of commercial-scale PV manufacturing capacity is new construction (greenfield), meaning it is purpose-built on an unused piece of land; however, there are alternatives. This paper will outline opportunities for re-use of existing obsolete semiconductor fabs, and the steps required to convert from one manufacturing strand to another.

Three buzzwords dominate the discussion about the future of the photovoltaic market in the U.S. right now: ITC (investment tax credit), credit crunch, and Obama. All three have the potential to shape how the solar industry will look in the next decades. Primary data results from EuPD Research show that after a year that featured much wailing and gnashing of teeth, market participants are now “realistically optimistic” on the prospects for the industry, despite the influence of the international credit crisis.