An efficient and deterministic photon management using deep subwavelength features. (April 2020)

• Record Type: Journal Article
• Authors: Prajapati, Ashish; Llobet, Jordi; Antunes, Mariana; Martins, Sofia; Fonseca, Helder; Calaza, Carlos; Gaspar, João; Shalev, Gil
• Is Part Of: Nano energy. Volume 70(2020)
• Publication Date: 2020-04
• Subjects: Light trapping -- Nanopillar arrays -- Broadband absorption of solar radiation -- Deep subwavelength structures -- Metamaterials; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2020.104521
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Light trapping and the broadband absorption of the solar radiation are significant to a plethora of absorption-based photonic devices. Specifically, efficient broadband absorption was recently demonstrated with arrays of subwavelength structures. The current study examines both numerically and experimentally light trapping driven by deep sidewall subwavelength structures (DSSS) in silicon nanopillar (NP) arrays (DSSS arrays). Particularly, the focus is on DSSS geometries that are an inherent outcome of the top-down dry etch approach used in arrays of high aspect ratio NPs due to the periodical operationality of the Bosch dry etch method. ~10% enhancement in the broadband absorption of DSSS arrays compared with NP arrays is demonstrated numerically, as well as the generation of near-IR absorptivity peaks of ~25% for DSSS arrays. Importantly, it is shown that the introduction of DSSS systematically blue-shifts the absorptivity peaks of the NP arrays and in this manner a deterministic light trapping is possible. Finally, decrements of ~40% in direct reflectivity and ~7% in diffused reflectivity in DSSS arrays realized on silicon wafers is demonstrated experimentally. Graphical abstract: Image 1 Highlights: Light trapping driven by deep sidewall subwavelength structures (DSSS) in silicon nanopillar arrays (DSSS arrays). Broadband absorption enhancement of ~10% in DSSS arrays compared with nanopillar arrays. The presence of DSSS induces the generation of near-IR absorptivity peaks of ~25%. DSSS blue-shifts the absorptivity peaks of the nanopillar arrays and allows semi-deterministic light trapping. We experimentally show a decrement of ~40% in direct reflectivity and ~7% in diffused reflectivity in silicon DSSS arrays.