Mechanical Engineering Undergrad here: So this didn't seem explicitly like a homework question, but I was wondering how to describe a solar cell in terms of thermodynamics. If I had to model it with the first law of thermodynamics, I would consider it a simple loop of heat/work exchange, idealizing the model to neglect kinetic energy, potential energy, and change in altitude. That just seems a little bit simplistic for me because the actual cell has activity going onto inside of it. The materials within the cell have holes for electrons to pass through. The electrons move when photons pass through the crystal-structure of the cell. This is the current and friction is neglected here, but that's also where some of the heat-loss comes from (I believe) and then loss of energy when the band gap(?) can't receive excess eV delivered by the photons. So a 3eV ray would lose 1.6eV in a 1.4eV system. So I would model my first law as such: Qin - W - Qout = 0 Where W = the work of charging a battery. Does my understanding sound precise? I'm asking here because I can't afford journals and it seems like my search results in either solar cell distributors (bias info) or academic journals (too technical and costs money).