Silica aerogel as rear reflector in silicon heterojunction solar cells for improved infrared response

Silicon (Si), with its indirect bandgap, is a non-ideal absorber. Thus, various strategies to boost silicon solar cells' efficiency, including advanced texturing, multilayer anti-reflecting coating, and rear reflectors are utilized. Dielectrics, deposited at elevated temperatures under a vacuum environment, are currently used to reduce the parasitic metal absorption at the rear. This work demonstrates that solution-based silica aerogel thin film is a flawless candidate for rear reflectors due to cost-effective deposition and near unity refractive index. We demonstrate that the morphology of aerogel thin films, spin-coated at room temperature under an ambient atmosphere, can be controlled by altering the solution concentration and spin-coating speed. We demonstrate -0.25 mA cm-2 short-circuit current density gain in the near-infrared region compared to cells with optimized indium zirconium oxide rear reflectors. Additionally, we show that incorporating aerogel in silicon heterojunction solar cells reduces the overall indium consumption required for TCO by more than 50%.