How a silicon solar cell powers a circuit

A light converter made from a semiconductor

A crystalline-silicon solar cell uses a processed wafer, surface layers and contacts to turn absorbed light into electrical power. Silicon alone does not define the function: logic chips use controlled switching to process signals; solar cells collect light-generated charge. The supplied energy comes from the light.

Source: DOE: photovoltaic cell basics ↗

From a photon to current through a load

A sufficiently energetic absorbed photon can create an electron–hole pair. A hole is a missing electron acting as a positive carrier. The junction helps separate them; recombination can prevent collection.

Source: NREL: Basic Photovoltaic Principles and Methods ↗

Selective contacts favour one carrier type and limit recombination losses. A closed external circuit lets the cell power a load. An open circuit can have voltage without sustained external current.

Source: National Laboratory of the Rockies: carrier-selective contacts research ↗ · DOE: photovoltaic cell basics ↗

Original p–n teaching diagram, not to scale. Green: external conventional current, opposite electron motion. Real cell layers vary.

Cell, module, array and inverter

Cell: One photovoltaic converter.
Module / panel: Interconnected cells with protective packaging.
Array: Connected modules.
Inverter: Converts DC electricity to AC; it does not create extra energy.

Source: DOE: cells, modules, arrays and systems ↗

Series-connected cells share current, so a shaded cell can restrict a string. Bypass diodes can route current around a cell group under suitable conditions, reducing available voltage. They do not recover the missing sunlight. Shade losses depend on the wiring, diode arrangement and operating point; “half the area shaded means half the power” is not a general rule.

Source: NREL: partially shaded PV operation ↗

Calculate power, then ask what was measured

Illustrative simultaneous measurements: load voltage 0.50 V and current 0.20 A give P = V × I = 0.10 W. Voltage and current must describe the same operating point; open-circuit voltage multiplied by short-circuit current does not give actual load power.

If incident light power on the measured area is 0.50 W, efficiency at that operating point is 0.10 ÷ 0.50 = 20%. Reflection, heat and recombination account for losses. Power is a rate in watts; efficiency is a ratio.

Source: DOE: photovoltaic performance and efficiency ↗

See the industrial making process →

Sources and further reading

Original teaching diagram and arithmetic examples. The illustrated p–n structure is one example; modern cell architectures vary.