Influence of TiO₂ nanostructures on the optical absorption of organic-inorganic perovskite

This work aims to reveal the strong influence of TiO₂ nanostructures on the light absorption property of TiO₂ and perovskite mixture. Three TiO₂ nanostructures, i.e., nanoparticles (S1), ultrapure nanorods (S2), and ultrasmall nanorods (S3), were studied: S1 was selected as a baseline; S2 and S3 were synthesized from S1 by using modified hydrothermal processes. Mesoporous TiO₂ thin films were spin-coated from solutions containing these TiO₂ nanorods and nanoparticles (S1 as baseline). Organic-inorganic hybrid perovskite CH₃NH₃PbI₃ was then incorporated into these mesoporous TiO₂ thin films. Optical absorption results showed that the perovskite mixture with ultrasmall TiO₂ nanostructures (S3) has significantly higher optical absorption coefficient. Finite-difference time domain models were built based on three distinct nanostructures of TiO₂ and CH3NH3PbI3 mixtures fabricated (S1 to S3) to understand their optical absorption properties. Our work is promising to fabricate TiO₂ nanostructures, as a backbone structure, for a series of applications including photovoltaics and photodetection.