Micro- and nano-scale optical focusing for carrier management in silicon solar cell

Well-designed nanostructures enable increased light trapping, reducing the loss of single-pass absorption and providing precise control over the microscale optical field, offering promising opportunities for developing nextgeneration high-efficiency solar cells. However, whether efficient carrier management in photovoltaic devices can be achieved by controlling electromagnetic field distribution using nanostructures remains elusive. In this study, we conducted simulations to investigate this issue and demonstrated the mechanism of micro- and nanoscale optical focusing in suppressing carrier recombination and enhancing the efficiency of silicon solar cells. By keeping the optical absorption of the silicon solar cell unchanged, under microscale light focusing conditions, we observed a relative 15.3% increase in the short circuit current compared to the Lambert law, resulting in a relative efficiency enhancement of 16.3%. Analysis of energy band, carrier density, recombination current, drift and diffusion current, and carrier mobility were conducted to reveal the recombination suppression mechanism. These findings comprehensively explain previously reported experimental results using wavelength-scale dielectric nanospheres to enhance the silicon solar cell efficiency. Furthermore, the implementation of nanoscale optical focusing offers the potential to significantly reduce the thickness of the device while maintaining high efficiency.