Doubling the Near‐Infrared Photocurrent in a Solar Cell via Omni‐Resonant Coherent Perfect Absorption

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, it is shown 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 660–740 nm where every wavelength resonates. These results may pave the way to transparent solar cells that optimally harvest near‐infrared light.

Broadband Omni-resonant Coherent Perfect Absorption in Graphene

“…The key to harnessing the resonantly enhanced optical absorption associated with CPA over a broad, continuous bandwidth -rather than only at discrete resonant wavelengths -is the notion of omniresonance [49][50][51][52][53], which is illustrated in Fig. 1.…”

“…Our previous work on CPA using the configuration shown in Fig. 1(c) assumed 'distributed' absorption; that is, the single-pass absorption A results from a layer in which absorption extends uniformly over its thickness L [5,18,19,50]. This assumption no longer holds for 'localized' absorption (such as a 2D material like graphene or a metasurface).…”

“…The re-orientation of the resonance trajectory in wavelength-angle (λ.ψ) space is a consequence of the angular dispersion introduced into the incident field. Moreover, note that each achromatic resonance extends in bandwidth across multiple free spectral ranges of the bare cavity [49][50][51].…”

“…This paper is organized as follows: first, we briefly review the concept of omni-resonance in the context of symmetric transparent FP cavities [49] and asymmetric FP cavities incorporating a partially absorbing layer [50]. Next, we describe theoretically the distinction between two scenarios of 'distributed' and 'localized' absorption.…”

Coherent Perfect Absorption in Tavis-Cummings Models

“…Fueled by the aforementioned notable developments, the CPA has shown several important applications in the past decade. Examples include photodetection instrumentation [16], solar cells [17], switches [18], microwave & radiowave antennas [19], sensors [20], and logic operators [21], to name a few. Entering the quantum domain, an immediate application of CPA turns out to be in the storage of quantum information that is encoded in different photonic degrees of freedoms [22].…”