Photon Recycling in a Solar Cell With Two Lambertian Surfaces

An exact analytical expression for the probability of photon reabsorption and recycling in an idealized solar cell with two Lambertian surfaces is derived. The existing approximations are found to agree with the exact formula to within 5%. The most accurate approximation turned out to be the simplest one that sets the reabsorption probability to the weak-absorption limit of the cell absorptance. The maximal photoconversion efficiency of a silicon solar cell is evaluated to be 29.5% at the base thickness of 98 $\mu$ m.