Physics / mechanism
Cadmium telluride (CdTe) is a II-VI compound semiconductor with a direct bandgap of ~1.45 eV — near-optimal for single-junction solar conversion under the Shockley-Queisser limit. Polycrystalline thin-film deposition (typically close-space sublimation or vapor transport) enables low-cost, large-area manufacturing. Minority carrier lifetime and grain boundary passivation are the dominant efficiency levers. First Solar holds the commercial benchmark at ~22.3% module efficiency; lab cells have hit ~22.6%. CdTe also serves in radiation detection (nuclear, medical imaging) where its high atomic number and ~1.6 eV bandgap at room temperature allow direct X-ray/gamma conversion without cryogenic cooling. Detector-grade CdTe and CdZnTe (CZT) require near-perfect single crystals, driving entirely different supply chains from photovoltaic CdTe.
Competitive landscape
CdTe competes directly with crystalline silicon (c-Si) in utility-scale PV and with CIGS in thin-film. In radiation detection, CZT, silicon drift detectors, and scintillator+PMT combinations are the main alternatives. Perovskites are a long-run threat across both applications.
| Technology | Efficiency (module) | Cost driver | Key weakness |
|---|---|---|---|
| CdTe | ~22% | Deposition throughput | Cd toxicity / Te scarcity |
| CIGS | ~19% | Sputtering complexity | Multi-element composition control |
| c-Si (mono) | ~23–24% | Wafer cost | CapEx, thickness |
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.