We use nonimaging, statistical-ray optics and ray-tracing simulations to study external light traps as a cost-effective means to enhance the absorption of optically imperfect solar cells. Our main finding is that the optical performance of a cell may be compromised substantially without affecting its overall performance if a trap is being used. As a result, simpler cell construction that gives better charge-transport abilities may be considered. As a case study, we show that the thickness of a silicon cell may be reduced to less than a micron without compromising its efficiency and that the efficiency of perovskite cell may increase substantially, almost up to its theoretical limit.
The paper reports on the scattering properties of different submicron mesoporous TiO2 structures and their correlation with the efficiency of photovoltaic devices. Bruggeman’s effective medium theory was used to calculate the effective refractive index. T-matrix and Mie theory were used to evaluate scattering parameters, such as scattering coefficient and asymmetry factor. The parameters presented here can be used either to understand the suitability of these TiO2 structures for photovoltaic and photocatalysis applications or as inputs for full optoelectronics simulation of devices. Scattering coefficients of the structures were found to mainly depend on their volume and porosity rather than shape. The dimensions and refractive index of scattering structures commonly used for photovoltaic and photocatalytic application are generally within a range of dimensions and refractive indices quite similar to that discussed in this paper, and hence, results discussed will also be indicative for other scattering structures for the same application. The effects of shape, size, and porosity on scattering parameters have also been discussed.