Cadmium Telluride Solar Cells (CdTe): advantages

The Cadmium Telluride (CdTe) solar technology was pioneered in the early stages of solar energy development, when Bonnet and Rabenhorst created the CdS/CdTe heterojunction, enabling the efficient manufacturing of CdTe solar cells. Initially, these panels achieved an efficiency of only 6%, but today, this figure has significantly increased to around 19%, with some records showing efficiencies as high as 22.1%.

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Major corporations like Kodak and First Solar have invested heavily into research centered around Cadmium Telluride technology. Today, CdTe remains the most favored thin-film solar panel technology, widely adopted by top manufacturers globally.

This article explores the various facets of CdTe solar panels, highlighting the materials involved, the manufacturing process, and possible applications while comparing CdTe to other solar technologies.

What is a Cadmium Telluride (CdTe) solar panel?

Cadmium Telluride solar panels are recognized as the leading type of thin-film solar panels on the market, accounting for approximately 5% of the total global solar panel market, second only to crystalline silicon panels.

For investors, one of the main attractions of CdTe thin-film solar panels lies in their cost-effective manufacturing process. Average efficiencies around 19% reflect their competitive edge, while laboratory breakthroughs have yielded efficiency records of 22.1% for CdTe solar cells.

In understanding CdTe thin-film solar panels, we can better appreciate their advantages and various applications. This section will delve into the materials and manufacturing processes pertinent to CdTe solar technology.

Materials used in CdTe thin-film solar cells and panels

CdTe cells utilize semiconductors designed to optimize the conversion of solar radiation to electricity. They comprise p-n heterojunctions, featuring a p-doped Cadmium Telluride layer and an n-doped Cadmium Sulfide (CdS) layer. In some applications, magnesium zinc oxide (MZO) may also be employed.

While these materials are affordable, there are environmental considerations to keep in mind. Greenpeace has issued caution regarding the toxicity of specific materials, revealing that CdTe panels contain 6g/m2 of hazardous metals and emit cadmium at levels around 0.5g/GWh. There are serious health implications tied to these substances.

Manufacturing process of CdTe thin-film solar panels

The manufacturing of CdTe thin-film solar panels integrates three core components: a semiconductor layer, a conductivity layer, and a protective layer:

• Photovoltaic material
• Conductive sheet
• Protective layer

Each segment plays a crucial role in the functionality of CdTe thin-film solar panels. Manufacturing employs various deposition techniques, with methods such as sputtering, chemical spray pyrolysis, and close vapor transport (CVT) being common.

Photovoltaic material

The photovoltaic material, responsible for converting solar radiation into DC energy, comprises a p-n heterojunction achieved through layered deposition of CdTe and CdS or MZO.

Conductive sheet

The conductive component facilitates energy flow between the solar cells, thus boosting voltage and enabling integration into photovoltaic (PV) systems. Typically, metal layers or carbon paste (often incorporating copper) are utilized in this layer.

Protective layer

Due to their fragile nature, photovoltaic layers must be safeguarded with a protective element. Rather than the traditional glass and aluminum frames, a Transparent Conductive Oxide (TCO) layer is employed for its durability, utilizing materials such as SnO2:F.

CdTe solar panels vs. Other types of thin-film panels

Within the thin-film arena, CdTe solar panels exist alongside several competitors:

• Amorphous silicon (a-Si) solar panels
• Copper indium gallium selenide (CIGS) solar panels
• Gallium arsenide (GaAs) solar panels

This article will further detail differences in materials, efficiency ratings, applications, and distinctive features of each technology.

Amorphous silicon (a-Si) vs. CdTe solar panels

A-Si thin-film panels rank lower in efficiency compared to CdTe, typically yielding around 6-7%. Although they are produced at a lower cost and feature reduced toxicity, their primary use tends to be in smaller-scale applications. Recent innovations suggest potential future developments could enable integration into wearable technology.

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Copper indium gallium selenide (CIGS) vs. CdTe solar panels

Though less toxic than CdTe, CIGS solar panels harbor moderate respiratory risks. They achieve efficiencies of about 12-14%, with research indicating potential laboratory peaks at 20.4%. While production expenses trail behind that of CdTe, innovative processes aim to reduce costs further.

The ease of installation contributes to CIGS panels being used in facade and window applications and offers promising potential for space-related projects.

Gallium arsenide (GaAs) vs. CdTe solar panels

GaAs solar panels boast an impressive efficiency rating of 28.8%, outpacing CdTe but come with much higher production costs. Slightly less toxic than CdTe, GaAs remains a semiconductor of concern due to its moderate health implications. Manufacturing GaAs involves complex processes, making large-scale deployment less common, focusing primarily on spacecraft and specialized applications.

CdTe solar panels vs. Crystalline silicon solar panels (Pros and cons)

To ascertain the most suitable technology, we compare CdTe panels and traditional crystalline silicon solar technologies:

The significant cost advantage of producing CdTe panels—around $0.46/Watt compared to crystalline panels—is noteworthy, as is their robustness against temperature fluctuations, resulting in higher performance in challenging environments.

While crystalline panels offer superior efficiency, making them preferable for residential applications, CdTe panels present numerous benefits for commercial solar farms, particularly within warmer climates, where CdTe technology might provide higher power outputs.

CdTe panel application: When to use CdTe solar panels?

Despite limited applicability for residential use, CdTe panels excel across a variety of commercial and industrial settings. Their lower initial cost of 70% less than crystalline alternatives makes them well-suited for extensive solar farm installations that capitalize on available land.

Adaptability is another strong point for CdTe technology, with potential applications extending to the integration of solar cells into construction materials, UAVs, and even emerging electric vehicles (EVs), offering innovative solutions for future energy needs.

Final words

There is no question that CdTe technology holds a prominent position within the thin-film solar panel landscape. The advantages of low cost, lightweight construction, durability, and simplified manufacturing process make CdTe ideal for numerous applications.

Although more prevalent in commercial and industrial sectors, continued advancements point towards a promising future for CdTe panels, with potential adoption across various platforms, including electric vehicles and specialized space applications.

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