Photovoltaic cells

I don't know too much about the subject, but hopefully I can point you in the right direction:
From a thermodynamic perspective, photovoltaics are analyzed based on exergy. Exergy is defined as the the maximum amount of work that can possibly be done during a process that brings the system into equilibrium with a heat reservoir.
So when the heat reservoir is the surrounding areas of a system, exergy can be defined as the potential of a system to cause changes as it reaches equilibrium.

This all comes into play with photovoltaics because of the fact that exergy accounts for the irreversibility of a thermodynamic process due to increases in entropy of the system. Energy cannot be destroyed, whereas exergy can be destroyed. The destruction of the exergy is proportional to the increase in entropy of the system. Remember, though, that exergy is not a thermodynamic property per se, but is a reference frame or a co-property of a system. So exergy and energy can be considered usable energy ratios.

However, forms of energy such as radiation and thermal energy cannot be converted completely to work, and have an exergy content less than their energy content. The exact proportion of exergy in a substance depends on the amount of entropy relative to the surrounding environment as determined by the 2nd law of Thermodynamics. I believe this efficiency is the same as carnot efficiency:
n = 1 - Tc/Th
And for the exergy of heat available:
B = Q(1- T_o/T_source)
Where Tsource is the temp of the heat source, and To is the temperature of the surroundings
The photovoltaic can alter the temperatures of its respective heat reservoirs using solar energy. I hope this gives you some ideas