Note:
The $P_{\mathrm{m}\mathrm{a}\mathrm{x}}$ value is obtained from the cell volt-ampere characteristic as the maximum of the product $V\cdot I=P$. Note that the product $V_{\mathrm{o}\mathrm{c}}\cdot I_{\mathrm{s}\mathrm{c}}$ is not a theoretical maximum output power of the cell, since the product is zero at both these values as $I=0$ for the open circuit and $V=0$ for short circuit.