Photovoltaic devices, i.e. solar cells, convert the energy in light into power, as electricity,
through light-driven generation of current and voltage.
a. Why does the efficiency of a solar cell increase, and then decrease, as the bandgap of the
light-absorber increases?
b. When one increases the irradiance incident on a solar cell from that of terrestrial solar
illumination (i.e. 1 Sun) to 100 times more intense illumination (i.e. 100 Suns), how do the
steady-state concentrations of species change, and what impact does that have on the
power-conversion efficiency?
c. You observe that as you decrease the thickness of the light-absorber, the excited-state
lifetime decreases and the open-circuit photovoltage remains the same. Please explain these
observations.
