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The maximum power point is the operating voltage $V_{\mathrm{mp}}$ and output electric current $I_{\mathrm{mp}}$ at which a source delivers its largest electrical power, $P_{\max }=V_{\mathrm{mp}}{I}_{\mathrm{mp}}$. It is found along the device's current–voltage curve under specified illumination and temperature.

For a smooth solar-cell output curve written with delivered current positive, an interior maximum satisfies $d(VI)/dV=I+VdI/dV=0$. The short-circuit current and open-circuit voltage are useful endpoints but neither delivers power, because one factor is zero at each endpoint. Changing illumination or temperature moves the maximum power point, motivating maximum power point tracking in the connected power converter.

At fixed spectrum and temperature, photocurrent is approximately proportional to irradiance, so the magnitude of short-circuit current increases nearly linearly. In the ideal model,so open-circuit voltage rises only logarithmically with irradiance. More incident optical power generally raises the maximum electrical power, within the device's thermal and resistive limits.

Increasing temperature strongly increases the dark saturation electric current. In silicon this normally reduces open-circuit voltage and maximum power, despite a small increase in short-circuit current associated with the temperature dependence of absorption and band gap. The thermal-voltage factor alone is insufficient to predict the sign; the temperature dependence of $I_0$ matters.

maximum power point tracking adjusts the load seen by the cell as irradiance and temperature change. A controlled DC–DC converter can transform the external load so that operation stays near the changing maximum of $-VI$, instead of at the generally suboptimal intersection with a fixed load. It matches operating conditions and cannot generate additional energy beyond the photovoltaic output.