Optimizing metal grating back reflectors for III-V-on-silicon multijunction solar cells

Multi-junction solar cells allow to utilize sunlight more effectively than single junction solar cells. In this work, we present optical simulations of III-V-on-silicon solar cells with a metal grating at the back, which experimentally have reached more than 33% power conversion efficiency. First, we perform simulations with the finite element method and compare them with experimental data to validate our model. We find that accurately modeling the investigated geometrical structure is necessary for best agreement between simulation and experimental measurements. Then, we optimize the grating for maximized light trapping using a computationally efficient Bayesian optimization algorithm. The photo current density of the limiting silicon bottom cell is improved from 13.48 mA/cm(2) for the experimental grating to 13.85 mA/cm(2) for the optimized metal grating. Investigation of all geometrical optimization parameters of the grating (period, height, . . .) shows that the structure is most sensitive towards the period, a parameter highly controllable in manufacturing by inference lithography. The results show a pathway to exceed the current world record efficiency of the III-V-on-silicon solar cell technology. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

Automated summary

This work presents optical simulations of III-V-on-silicon solar cells with a metal grating for improved light trapping efficiency. The study demonstrates that the period of the grating is a critical parameter affecting its performance, which can be highly controlled during manufacturing using inference lithography. The results suggest a pathway to exceed the current world record efficiency of the III-V-on-silicon solar cell technology.