An Optical Model for Predicting the Quantum Efficiency of Solar Modules

The fact that a solar cell will be encapsulated in a solar module has a strong impact on how its optical properties should be characterized, designed, and optimized. In this paper, we present a ray-tracing model that is capable of calculating the optical properties of a solar cell with a random pyramidal texture both with and without encapsulation and for the light at any angle of incidence. We introduce a simple method wherein we combine ray tracing and external quantum efficiency (EQE) measurements of a solar cell to predict the EQE after encapsulation for any choice of encapsulation materials and antireflection coatings. We verify the quality of our EQE-prediction toward experimental data and find good agreement. We apply this approach and compare the influence of different encapsulation materials on the module performance and perform a full loss analysis at a few selected angles of incidence. Finally, we use the ray-tracing model to map generation current for all angles of incidence relevant for a pyramidal texture both with and without encapsulation.