Asked by qp
Photovoltaic cells absorb sunlight and use it to generate electricity. What energy is involved in this process?
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The energy involved is the electromagnetic energy of sunlight — i.e. photons.
Photovoltaic cells work by absorbing photons whose quantum energy E = hf (or E ≈ 1240/λ in nm, in eV). If a photon’s energy is greater than the semiconductor’s band gap (for silicon ≈ 1.12 eV) it can excite an electron from the valence band to the conduction band, creating an electron–hole pair. The cell’s internal electric field separates these charges, turning the photon’s energy into electrical potential energy and current. Part of the absorbed energy is lost as heat (thermalization, recombination, resistive losses), so not all photon energy becomes usable electricity.
Typical visible-photon energies are ~1.6–3.1 eV; typical peak solar irradiance at earth’s surface is ≈1000 W/m².
Photovoltaic cells work by absorbing photons whose quantum energy E = hf (or E ≈ 1240/λ in nm, in eV). If a photon’s energy is greater than the semiconductor’s band gap (for silicon ≈ 1.12 eV) it can excite an electron from the valence band to the conduction band, creating an electron–hole pair. The cell’s internal electric field separates these charges, turning the photon’s energy into electrical potential energy and current. Part of the absorbed energy is lost as heat (thermalization, recombination, resistive losses), so not all photon energy becomes usable electricity.
Typical visible-photon energies are ~1.6–3.1 eV; typical peak solar irradiance at earth’s surface is ≈1000 W/m².
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