Solar cells are made of

Question

Examoogle · Accepted Answer

Silicon

Explanation: Solar cells (photovoltaic cells) are primarily made from semiconductor materials, with crystalline Silicon being the industry standard due to its abundance and bandgap properties. These devices convert sunlight directly into electricity via the photovoltaic effect.

Working Principle: When photons with energy $E = h
u$ greater than the semiconductor bandgap energy $E_g$ strike the Silicon, they excite electrons from the valence band to the conduction band. This creates electron-hole pairs, which are separated by the internal electric field of the p-n junction, generating a DC current across the external load.

Key Formulas: $E = h
u = \frac{hc}{\lambda}$ — Energy of incident photons; $E_g \approx 1.1 	ext{ eV}$ — Bandgap energy of Silicon at 300K

Key Points: Silicon is an indirect bandgap semiconductor.; The efficiency of a single-junction silicon cell is limited by the Shockley-Queisser limit.; Doping agents like Phosphorus (n-type) and Boron (p-type) are used to create the p-n junction.

Advantages: High abundance of silicon in the Earth's crust; Excellent long-term stability and environmental durability

Disadvantages: Low energy conversion efficiency for single-junction cells; High-temperature sensitivity reduces voltage output

Applications: Residential and industrial solar panels; Spacecraft and satellite power systems

Additional Info: Silicon is preferred over Germanium because Silicon has a more suitable bandgap ($1.1 	ext{ eV}$ vs $0.67 	ext{ eV}$) for solar spectrum harvesting and better thermal stability.. Option B (Germanium) is used in multijunction cells but is too costly for standard panels. Option C (Silver) is used for conductive contacts, not the semiconductor body.

Answer: A is correct — Silicon is the most widely used semiconductor material for fabricating efficient, stable, and cost-effective photovoltaic cells.

Exam Tip: Always remember that while Silicon is standard, the bandgap energy $E_g$ must be optimal (typically 1.0–1.5 eV) to match the solar spectrum peak; this is why materials like GaAs are also highly efficient.

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