Fundamental Limit of Nanophotonic Light-trapping in Solar Cells

TL;DR

This paper develops a new electromagnetic theory that surpasses traditional limits of light trapping in solar cells by exploiting deep-subwavelength optical mode confinement, promising more efficient solar energy devices.

Contribution

It introduces a statistical temporal coupled-mode theory for nanophotonic light trapping, extending beyond classical limits and enabling higher absorption in solar cells.

Findings

Standard light trapping limit can be exceeded in nanophotonic regimes

Deep-subwavelength mode confinement enhances absorption

New theoretical framework guides next-generation solar cell design

Abstract

Establishing the fundamental limit of nanophotonic light-trapping schemes is of paramount importance and is becoming increasingly urgent for current solar cell research. The standard theory of light trapping demonstrated that absorption enhancement in a medium cannot exceed a factor of 4n^2/ sin^2(\theta), where n is the refractive index of the active layer, and \theta is the angle of the emission cone in the medium surrounding the cell. This theory, however, is not applicable in the nanophotonic regime. Here we develop a statistical temporal coupled-mode theory of light trapping based on a rigorous electromagnetic approach. Our theory reveals that the standard limit can be substantially surpassed when optical modes in the active layer are confined to deep-subwavelength scale, opening new avenues for highly efficient next-generation solar cells.