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

Area of Science:

• Materials Science
• Renewable Energy
• Optoelectronics

Background:

• Multi-junction solar cells offer superior sunlight utilization compared to single-junction designs.
• III-V-on-silicon solar cells have experimentally achieved over 33% power conversion efficiency.

Purpose of the Study:

• To perform optical simulations of III-V-on-silicon solar cells with back metal gratings.
• To validate simulation models against experimental data.
• To optimize grating geometry for enhanced light trapping and improved photocurrent.

Main Methods:

• Finite element method (FEM) simulations were employed.
• Models were validated by comparing simulation results with experimental data.
• Bayesian optimization was used to efficiently optimize grating parameters.

Main Results:

• Accurate modeling of the geometrical structure is crucial for simulation-experimental agreement.
• Optimized metal gratings increased the photocurrent density of the silicon bottom cell from 13.48 mA/cm² to 13.85 mA/cm².
• Grating period was identified as the most sensitive parameter for optimization, controllable via nanoimprint lithography.

Conclusions:

• The study demonstrates a method for enhancing light trapping in III-V-on-silicon solar cells.
• Optimization of back metal gratings offers a viable pathway to surpass existing efficiency records.
• Precise control over grating geometry, particularly the period, is key to maximizing solar cell performance.