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Maximum power point tracking adjusts the electrical load presented to a source so that it operates near its maximum power point. In a photovoltaic system, a controlled power converter can change the panel's operating voltage while delivering energy to a battery or another load.

One elementary strategy perturbs the operating voltage, measures the resulting power, and continues in the direction that increases it. If illumination changes during the measurement, the power change may reflect the weather rather than the chosen perturbation, so the control must distinguish these effects over an appropriate time scale. Partial shading can also produce several local maxima in an array's power curve. Tracking changes the operating condition; it does not raise the power available on that instantaneous curve.

Absorbed photons with energy at least the band gap generate electron–hole pairs. The built-in field of the p-n junction separates carriers generated in or reaching the depletion region; minority carriers generated nearby can diffuse into that collection region. Selective contacts carry electrons and holes into an external circuit before they recombine.

Define positive electric current into the positive-voltage terminal. In the ideal illuminated-diode model,The dark curve has $I_{\mathrm{ph}}=0$; illumination shifts it downward. At short circuit $I\simeq -I_{\mathrm{ph}}$; at open circuit $I=0$ and $V=V_{\mathrm{oc}}$. Between them the illuminated cell lies in quadrant IV and supplies power $P_{\mathrm{out}}=-VI>0$. The maximum power point maximizes the area of the rectangle with sides $V$ and $-I$:It is neither the open-circuit point nor the short-circuit point, both of which supply zero power.

The short-circuit current is the terminal electric current of a device when its terminal voltage is zero. For a solar cell, it is usually denoted $I_{\mathrm{sc}}$ and is obtained from the illuminated current–voltage curve where the two terminals are connected through a sufficiently low-resistance measuring path.

A nonzero short-circuit current establishes photogenerated charge collection, but the delivered terminal power $P=VI$ is zero at an ideal short circuit. Useful electrical output instead requires a finite operating voltage, often near the maximum power point. The short-circuit current depends on illumination, active area and collection efficiency; short-circuit current density divides it by the specified area, allowing devices of different sizes to be compared.