Heating a solar cell subjected to incident solar irradiance is studied. Laplace Integral Transform technique is applied to get the temperature field within the cell. The efficiency as a function of the cell temperature is estimated, and its variation with the local day time is thus clarified. Different cooling levels are considered. An illustrative example is given. The results show that the diurnal temperature variation of the cell is significant, while the efficiency is revealed to be a slowly varying function of temperature along the day time. It is revealed that as the temperature of the cell increases the efficiency decreases. Thus shading and cooling conditions may be useful to increase its efficiency.