Synthesis and Formation of Hybrid Heterostructures Based on 1-D and 3-D TiO₂ and Selectively Doped Sputtered NiO Layers for Energy Harvesting Applications

In an attempt to identify solutions to advance net-zero energy actions and accelerate the deployment of cutting-edge low-carbon technologies, hybrid approaches of synthesizing and engineering materials towards solar energy harvesting and management have been developed. In this work, two different forms of TiO2 were synthesized and applied as electron transfer layer (ETL) in perovskite solar cells (PSCs). In addition, double-doped NiO was combined with these two forms of TiO2 and the fabricated NiO/TiO2 heterostructures were examined for their photocatalytic activities against decolorization of methylene blue (MB) probe-molecule pollutant. The two forms of TiO2 were the 1-D TiO2 nanorods (TiO2-NRs), synthesized by an aqueous hydrothermal technique, and the 3-D mesoporous TiO2 (m-TiO2), synthesized by spin-coating. The NiO was fabricated by sputtering and after doping-engineering the optimum double-doped NiO:(Nb,N) was used to form the NiO/TiO2 heterostructures. The PSC formed by the 1-D TiO2-NRs as ETL exhibited under AM1.5 illumination the same open-circuit voltage but twice the short-circuit current when compared to the PSC having the conventional m-TiO2 as ETL. The photocatalytic activity of the 1-D NiO/TiO2 heterostructure with the NRs was 23% faster than the respective 3-D NiO/TiO2 heterostructure, inducing at the same time around 83% more (MB) degradation. The effect of the increased effective surface area of the 1-D heterostructures employing the NRs, along with the enhanced NiO-TiO2 diode properties favouring and enhancing the absorption and the rates of photocatalytic reactions are discussed. These results provide a direct comparison between heterostructures synthesized via hybrid routes for optoelectronic applications in the fields of energy harvesting and photocatalysis.