Silicon solar cells reaching the efficiency limits: From simple to complex modelling

Numerical modelling is pivotal in the development of high efficiency solar cells. In this contribution we present different approaches to model the solar cell performance: the diode equation, a generalization of the well-known Hovel model, and a complete device modelling. In all three approaches we implement a Lambertian light trapping, which is often considered as a benchmark for the optical design of solar cells. We quantify the range of parameters for which all three approaches give the same results, and highlight the advantages and limitations of different models. Using these methods we calculate the efficiency limits of single-junction crystalline silicon solar cells in a wide range of cell thickness. We find that silicon solar cells close to the efficiency limits operate in the high-injection (rather than in the low-injection) regime. In such a regime, surface recombination can have an unexpectedly large effect on cells with the absorber thickness lower than a few tens of microns. Finally, we calculate the limiting efficiency of tandem silicon–perovskite solar cells, and we determine the optimal thickness of the bottom silicon cell for different band gaps of the perovskite material.