Computational analysis of solar light harvesting properties of TiO2-BiVO4 inverse opals for applications in photocatalysis

Efficient solar light harvesting is essential for high-performance photocatalysts. Here, Rigorous Coupled-Wave Analysis (RCWA) computational method is used to investigate and optimize the optical absorption of TiO2-BiVO4 inverse opal (IO) structures under varying light incidence angles and pore-filling medium (air or water). Simulations were validated against experimental reflectance data. They revealed that small-pore IOs strongly absorb in the UV-C and UV-B regions due to the slow photon effect, making them ideal for sterilization and water disinfection. Medium- and large-pore IOs benefit from additional slow photon effect at the 2nd order photonic band gap, enhancing absorption across both UV and visible regions. Medium-pore IOs are suited for indoor air treatment and water purification, while large-pore IOs with the highest photon flux enhancement enable solar-driven photocatalysis such as outdoor pollutant removal and hydrogen production. For all tested IO designs, the absorbed photon flux exceeds that of equivalent planar slabs, highlighting the advantage of photonic structuring for sustainable photocatalytic applications.