Enhancing performance of perovskite solar cells with efficiency exceeding 21% via a graded-index mesoporous aluminum oxide antireflection coating.

Antireflection (AR) film is a widely used technology to enhance the performance of photovoltaic devices that require transparent electrodes in the photovoltaic industry. At present, several AR films including monolayer MgF₂ or multilayered composite films, textured polydimethylsiloxane (PDMS) and porous SiO₂ have been successfully applied due to their excellent properties. Nevertheless, all of the above-mentioned AR films have some minor drawbacks to overcome, for instance, the cost or thermal durability. Herein, we report a cost-effective and low-temperature method to fabricate a mesoporous aluminum oxide (meso-Al₂O₃) layer as the AR coating with high thermal durability, which will meet the fabrication condition of various photovoltaic devices. Briefly, the process begins at magnetron sputtering a compact Al₂O₃ film, which shows no AR effect, followed by a hot water treatment at 80 °C to turn the compact film into a mesoporous film with graded-index and AR effect. The application of meso-Al₂O₃ AR film enhances the maximum transmittance of our laboratory-used fluorine-doped tin oxide (FTO) from 84% to 89%, which is in good agreement with our theoretical simulation named graded-index approximation. Taking perovskite solar cells (PSCs) as an example, planar PSCs with meso-Al₂O₃ AR film deliver excellent photon conversion efficiency of 21.5%, which is higher than that of cells without meso-Al₂O₃ AR film (20.9%). [ABSTRACT FROM AUTHOR]