How do solar cells work diagram

2025-05-08

Solar cells operate via the photovoltaic effect, which for brevity's sake, I will refer to later as the solar effect. The photovoltaic effect is defined as light inducing a potential difference between different parts of an uneven semiconductor, or semiconductor with a metal.

The specific working principle of solar cells, follows:

When sunlight simply hits the surface of a semiconductor, the valence electrons of atoms such as in the N and P regions inside the semiconductor receive energy exceeding the bandgap width through light radiation (the energy level of either the electron increases from valence band to conduction band) and break free from covalent bonds. Henceforth, non-equilibrium electron-hole pairs are created inside the semiconductor conversely if the non-equilibrium-electron-hole pairs recombine inside the semiconductor and the system in-balance, i.e. the semiconductor cannot convert recorded electrical-energy from the absorbed light energy, and value is lost freely by itself whom it absorbed light as hiding, hence the system cannot externally engender expansive electrical energy.

As such as to reach the objective of photoelectric conversion, then electrons and holes are separated precluding recombination in the semiconductor, hence cannot recombine any longer in the semiconductor.

The "potential barrier" electric field in the space charge region of the PN junction can be used to separate semiconductor electrons and holes. Once the photo-induced electron-hole pairs are created in the semiconductor by light, the electric field in the PN junction immediately separates the electrons and holes. The electrons are pushed into the N region and the holes pushed into the P region. Namely, there are excess electrons in the N region and excess holes in the P region. As a result, a photo-induced electromotive force opposite to the electric field of the "potential barrier" appears at each end of the PN junction.

When such semiconductors with a PN junction are fabricated into solar cells and connected to external loads, the photo-induced current flows from the P region through the load to the N region, allowing the load to output power.

The functionally core element of the solar cell is the PN junction, which acts like a wall from stopping the recombination between electrons and holes. When the solar cell is under sunlight and electrons in the solar cell absorbs light energy and moves into the N region, the N region becomes negatively charged, and the holes move into the P region and the P region becomes positively charged, and this produces a potential difference, or voltage, at the two ends of the PN junction.

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