Thin Film Photovoltaics
Torsten Brammer, Consultant, Photovoltaic Research and Consulting
The most prominent challenge in PV is the reduction of the initial investment. But the costs for power from PV also depend on the long-term stability of the components of a PV installation. All PV module technologies can degrade if the individual weaknesses are not considered for the solar cell process, encapsulation and installation. For crystalline silicon, the potential-induced degradation effect gains some attention these days. The Staebler-Wronski effect for amorphous silicon seems to be inherent for this material. Exposure to air and water can cause degradation for CdTe, CIGS, dye-sensitized and organic solar cells. In general, the presence of certain ions in an electric field, the presence of oxygen and water as well as weak bonds can cause a loss in power output of a PV panel.
Tim Young, HyperSolar Inc
The term “concentrated photovoltaics” (CPV) is confusing, even to many in the solar industry. And no wonder – the term is an umbrella one that includes widely varying technologies. To make matters worse, it is often confused with concentrated solar power (CSP) – or solar thermal – which is another animal altogether.
Torsten Brammer, Photovoltaic Research Consultant
When Applied Materials announced the discontinuation of their product SunfabTM, a fully integrated line for manufacturing thin film silicon solar panels, many took this as a clear signal that thin film silicon is not a viable technology. According to analysts, the material to work with is CIGS (new material that promises high efficiencies) and crystalline silicon (mature and dominant market share). CdTe is doing fine anyhow. While there are surely some facts that support this analysis, it is time to see if all facts are considered and to look at thin film silicon more closely.
This article has been restricted to registered FuturePV users. If you have an existing account, please log in. Otherwise, please register for a user account to view this article - REGISTRATION IS QUICK AND FREE.
Louay Eldada, HelioVolt Corporation
In recent years, thin film photovoltaic (PV) companies started realizing their low manufacturing cost potential, and have been grabbing an increasingly larger market share. Copper indium gallium selenide (CIGS) is the most promising thin film PV material, having demonstrated the highest energy conversion efficiency in both cells and modules. However, most CIGS manufacturers still face the challenge of delivering a reliable and rapid manufacturing process that can scale effectively and deliver on the promise of this material system. HelioVolt has developed a reactive transfer process for CIGS absorber formation that has the benefits of good compositional control and a fast, high-quality CIGS reaction. The reactive transfer process is a two-stage CIGS fabrication method. Precursor films are deposited onto substrates and reusable cover plates in the first stage, while in the second stage, the CIGS layer is formed by rapid heating with Se confinement. High-quality CIGS films with large grains were fabricated on the production line, and high-performance monolithic modules with a form factor of 120 cm x 60 cm were produced. With conversion efficiency levels around 14 percent for cells and 12 percent for modules, HelioVolt started commercializing the process on its first production line.
This article has been restricted to registered FuturePV users. If you have an existing account, please log in. Otherwise, please register for a user account to view this article - REGISTRATION IS QUICK AND FREE.
Danielle Merfeld, GE’s Global Research Center
Thin film PV continues to capture the attention of the industry with the promise of a departure from the “s-curve” described by the current c-Si PV technology era of solar. Today the range of thin film PV materials is wide and the approaches varied; however, the mantra for success is the same: Use technology to drive high efficiency at low cost. Some approaches are of particular interest based on the opportunity to deliver a high-efficiency product, as evidenced by recent lab-scale records. Others benefit from manufacturing scale and a community of researchers creating advancements on a well-known material system.
Luc Feitknecht, goMicromorph Ltd.
There was a wide-open window of opportunity for thin film solar modules based on amorphous silicon due to the shortage of crystalline silicon wafer material in 2005. The time of the soaring raw-material prices was over in 2010, and the price per watt of solar power plunged lower than expected some years ago. This is good news for the penetration of photovoltaics worldwide. But it presents some difficulty to some manufacturers of solar panels. So why the “crisis” and where to go next? In this article, the discussion centers around amorphous silicon and nanocrystalline silicon tandem solar cells specifically.
This article has been restricted to registered FuturePV users. If you have an existing account, please log in. Otherwise, please register for a user account to view this article - REGISTRATION IS QUICK AND FREE.
Robert Birkmire − Institute of Energy Conversion
Thin film solar technologies have emerged as a clear alternative to c-Si solar cell modules for many applications with both a-Si-based and CdTe modules leading the way. From a cost perspective, First Solar has demonstrated, for CdTe modules, how high-speed/high-throughput manufacturing coupled with minimum materials usage can dramatically reduce manufacturing costs. From a performance perspective, the efficiency of thin film modules is in the range of 6 to 13 percent, significantly less than c-Si modules. However, the annualized output, kW-hr/kW, for both a-Si and CdTe modules is comparable to c-Si modules, particularly in warm climates. CuInSe2-based modules are beginning to emerge with Solar Frontier developing a 900 MW factory and projecting module efficiencies over 14 percent by 2014. The thin film PV arena is rapidly changing and continues to gain market share with respect to c-Si.
Gregory M. Hanket, Institute of Energy Conversion, University of Delaware
Abstract
Champion thin-film device efficiencies by thermally co-evaporated Cu(InGa)Se2 argue for its implementation as a manufacturing approach. This article describes the engineering approaches utilized in addressing two challenges encountered at the commercial scale: large-area deposition uniformity and droplet ejection from evaporation sources.
This article has been restricted to registered FuturePV users. If you have an existing account, please log in. Otherwise, please register for a user account to view this article - REGISTRATION IS QUICK AND FREE.
Danielle Merfeld, GE’s Global Research Center
Like its “older brother” and mainstay of the solar industry, crystalline Si, thin film PV technology has been the focus of development for several decades. The Institute of Energy Conversion (IEC) was established at the University of Delaware in 1972, becoming the world’s first laboratory dedicated to thin film PV R&D. By 1980, researchers at IEC had demonstrated thin film solar cells (Cu2S/CdS) exceeding 10 percent efficiency, and today the PV industry leader is First Solar, a thin film (CdTe) module manufacturer. Key advances enabling this shift for thin film PV from lab demonstrations to market dominance include the development of robust commercial manufacturing processes.
Torsten Brammer, Sunfilm AG
The main commercial technologies in photovoltaics are based on wafers made of mono- and multicrystalline silicon, thin films made of CdTe, thin films made of CIGS and thin films made of silicon. The produced volume from all thin film plants in 2009 was around 1.6 GW with a share of around 0.6 GW for thin film silicon (for reference: the total installed power including all technologies in 2009 was around 7 GW*).
