Inverse Optical Cavity Design for Ultrabroadband Light Absorption Beyond the Conventional Limit in Low‐Bandgap Nonfullerene Acceptor–Based Solar Cells. Issue 20 (2nd April 2019)

• Record Type: Journal Article
• Authors: Liu, Quan; Toudert, Johann; Li, Tengfei; Kramarenko, Mariia; Martínez‐Denegri, Guillermo; Ciammaruchi, Laura; Zhan, Xiaowei; Martorell, Jordi
• Is Part Of: Advanced energy materials. Volume 9:Issue 20(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-04-02
• Subjects: light trapping -- low‐bandgap nonfullerene acceptor thin‐film solar cells -- optical cavity -- ternary blends; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201900463
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: In the subwavelength regime, several nanophotonic configurations have been proposed to overcome the conventional light trapping or light absorption enhancement limit in solar cells also known as the Yablonovitch limit. It has been recently suggested that establishing such limit should rely on computational inverse electromagnetic design instead of the traditional approach combining intuition and a priori known physical effect. In the present work, by applying an inverse full wave vector electromagnetic computational approach, a 1D nanostructured optical cavity with a new resonance configuration is designed that provides an ultrabroadband (≈450 nm) light absorption enhancement when applied to a 107 nm thick active layer organic solar cell based on a low‐bandgap (1.32 eV) nonfullerene acceptor. It is demonstrated computationally and experimentally that the absorption enhancement provided by such a cavity surpasses the conventional limit resulting from an ergodic optical geometry by a 7% average over a 450 nm band and by more than 20% in the NIR. In such a cavity configuration the solar cells exhibit a maximum power conversion efficiency above 14%, corresponding to the highest ever measured for devices based on the specific nonfullerene acceptor used. Abstract : A 1D ultrabroadband (>450 nm) optical cavity is designed following an inverse electromagnetic computational approach to optimally trap light in a thin film absorber layer. When this novel cavity concept is applied to a low bandgap organic solar cell, a broadband absorption enhancement is demonstrated beyond the conventional limit resulting from light trapping in an ergodic optical geometry.