Improvement of photon management in partial rear contact solar cells using a combination of DBR and Mie scatterers

In this article, we present systematic simulations and numerical analysis of a novel light trapping scheme in a partial rear contact (PRC) solar cell involving a combined effect of rear located Distributed Bragg Reflectors (DBRs) and Mie scatterers comprising of dielectric nanoparticles (DNP), thereby, enhancing the efficiency of the device. We have studied the effect of three different types of DBRs in combination with embedded silica (SiO2) DNPs which scatter light into silicon substrate of PRC c-Si solar cell. The materials for DBRs are chosen in such a way that they may serve the dual purpose of reflecting more than 90% of incident light at the rear surface and passivating it as well. The internal reflection from the rear surface, absorption enhancement ratio and average scattering angle have been computed from 3-dimensional finite difference time domain (FDTD) simulations and performing numerical analysis later on. Further, these results are used in the analysis of basic solar cell to extract the parameters like short circuit current density, open circuit voltage, fill factor, reverse saturation current density and efficiency of solar cell. It has been observed that significant increase in efficiency can be achieved for solar cells having 10-100 µm thick substrates by incorporating this light trapping scheme. Beyond 100 µm thickness, the conversion efficiency approaches a saturation value. Moreover, a combination of DBR with silica nanoparticles results in maximum efficiency near 50 µm thickness of solar cell thereby improving the baseline efficiency from ~20.3% to an absolute value of 22.9%. This study opens up a new perspective of light management using the advantages of highly reflective DBRs and highly scattering DNPs which can be incorporated in a rather simple and inexpensive way for thin (<100 µm) silicon solar cells.