- Cadmium telluride (CdTe) is an inorganic compound composed of cadmium and tellurium, belonging to the family of II–VI semiconductors.
- In its pure form, CdTe is a crystalline solid that can range from dark gray to black in appearance, depending on its form and purity. It crystallizes in the cubic zinc blende (sphalerite) structure, where each cadmium ion (Cd²⁺) is tetrahedrally coordinated to four telluride ions (Te²⁻), and each telluride ion is similarly coordinated to four cadmium ions. This arrangement gives CdTe distinct semiconducting properties, making it a key material in optoelectronic devices.
- Cadmium telluride is typically synthesized by directly combining cadmium and tellurium elements at elevated temperatures or by chemical vapor deposition methods for thin-film applications. It can also be prepared via solution-based routes for nanoparticle or quantum dot production, allowing for size-tuned optical properties through quantum confinement. As with other cadmium chalcogenides, the synthesis method greatly influences crystal quality, stoichiometry, and performance in electronic devices.
- One of CdTe’s most notable characteristics is its direct bandgap of about 1.45 eV, which is very close to the optimal value for converting sunlight into electricity according to the Shockley–Queisser limit. This makes CdTe an exceptionally efficient absorber material for thin-film solar cells, capable of achieving high conversion efficiencies with relatively low material usage. CdTe modules also perform well under low-light conditions and have good resistance to degradation from heat and moisture, which has led to their large-scale commercial deployment in photovoltaic systems worldwide.
- In addition to photovoltaics, CdTe is used in radiation detection equipment, including X-ray and gamma-ray detectors, due to its high atomic number and density, which give it excellent stopping power for high-energy photons. This property makes it valuable for medical imaging, security scanning, and scientific instrumentation. Furthermore, CdTe has applications in electro-optical modulators and infrared optical components. Nanostructured CdTe, such as quantum dots, is explored in optoelectronics and bioimaging, where its tunable emission properties are advantageous.
- Despite its technological benefits, cadmium telluride is hazardous due to the toxicity of cadmium and the potential health risks of tellurium compounds. Inhalation of dust or fumes can cause respiratory and systemic damage, and CdTe is considered potentially carcinogenic. Environmental contamination is also a concern, as cadmium can persist in ecosystems and bioaccumulate in living organisms. However, in solid CdTe form, the compound is relatively stable and less soluble than many other cadmium salts, reducing immediate bioavailability. Strict safety measures are still essential during manufacturing, handling, and disposal, and end-of-life recycling of CdTe solar modules is a critical aspect of sustainable usage to minimize environmental impact.
