Doubling the near-infrared photocurrent in a solar cell via omni-resonant coherent perfect absorption

TL;DR

This paper demonstrates that omni-resonance in a structured optical cavity can significantly enhance near-infrared absorption in thin-film silicon solar cells, doubling photocurrent across a broad spectral range and enabling more efficient, potentially transparent solar devices.

Contribution

It introduces the concept of omni resonance to achieve broadband coherent perfect absorption, overcoming the narrow bandwidth limitation of traditional resonant structures.

Findings

Near-infrared absorption doubles in the targeted spectral range.

Omni resonance decouples resonant bandwidth from cavity photon lifetime.

Enhanced absorption leads to increased photocurrent in thin-film solar cells.

Abstract

Minimizing the material usage in thin-film solar cells can reduce manufacturing costs and enable mechanically flexible implementations, but concomitantly diminishes optical absorption. Coherent optical effects can help alleviate this inevitable drawback at discrete frequencies. For example, coherent perfect absorption guarantees that light is fully absorbed in a thin layer regardless of material or thickness but only on resonance. Here we show that omni resonance delivers such coherent enhancement over a broad bandwidth by structuring the optical field to nullify the angular dispersion intrinsic to resonant structures. After embedding an amorphous-silicon thin film photovoltaic cell in a planar cavity, pre conditioning the incident light using an alignment free optical arrangement severs the link between the resonant bandwidth and the cavity photon lifetime, thereby rendering the cavity omni resonant. Coherently enhanced near infrared absorption doubles the photocurrent over the targeted spectral range 660 to 740 nm where every wavelength resonates. These results may pave the way to transparent solar cells that optimally harvest near infrared light.