High‐Performance and Low‐Cost Gradient Refractive Index Films for Ultra‐Broadband and Ultra‐Wide Angle Antireflective Applications

Abstract Gradient refractive index (GRIN) films have great potential for applications in photovoltaics, imaging, and other fields due to their excellent antireflective ability. However, the development of highly reproducible processes for large‐area GRIN film preparation remains challenging. Here, a novel method to fabricate GRIN nanoporous silica films is proposed using magnetron co‐sputtering of silica‐alumina composite multilayer films followed by single‐step selective wet etching with phosphoric acid. The GRIN film with excellent ultra‐broadband, ultra‐wide angle antireflective properties (average double‐sided reflection suppressed within 14.2% up to 70° for 400–2000 nm band), high reproducibility, and good environmental reliability is demonstrated. Furthermore, the photovoltaic glass covers prepared with this GRIN film are verified to help reduce the energy loss in solar cells.