Explore Module
Basic Level
From the junction to the circuit: current and voltage
When sunlight illuminates the cell, continuous photon absorption generates a steady supply of electron-hole pairs. The junction's electric field continuously separates these charges, driving electrons toward the N-side and holes toward the P-side.
When metal contacts are attached and connected through an external circuit, electrons flow from the N-side, through the circuit (powering a load), and return to the P-side to recombine with holes. This flow constitutes photovoltaic current.
The voltage produced by a single silicon cell is approximately 0.5–0.6 volts, determined by the bandgap energy and junction characteristics. Current depends on light intensity and cell area: more photons → more electron-hole pairs → higher current.
If a single cell produces only ~0.5V, how do solar panels generate useful voltages?
Multiple cells are connected in series (positive terminal of one to negative terminal of the next) to add voltages. A typical panel contains 60–72 cells in series, producing 30–40 volts under standard conditions.
Multiple cells are connected in series (positive terminal of one to negative terminal of the next) to add voltages. A typical panel contains 60–72 cells in series, producing 30–40 volts under standard conditions.