Fundamental limit of nanophotonic light trapping in solar cells

TLDR

The urgent need to establish the fundamental limit of nanophotonic light‑trapping schemes arises because the standard theory caps absorption enhancement at 4n²/sin²θ, a limit that does not hold in the nanophotonic regime. The study aims to develop a statistical temporal coupled‑mode theory of light trapping based on rigorous electromagnetic analysis. The authors construct the theory using a statistical temporal coupled‑mode framework that rigorously models electromagnetic interactions. The theory shows that the conventional limit can be substantially exceeded when optical modes exhibit deep‑subwavelength field confinement, opening avenues for highly efficient next‑generation solar cells.

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 4 n 2 / sin 2 θ , where n is the refractive index of the active layer, and θ 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 conventional limit can be substantially surpassed when optical modes exhibit deep-subwavelength-scale field confinement, opening new avenues for highly efficient next-generation solar cells.