Recent advancement of titanium dioxide electron transport layers for perovskite solar cells

Titanium dioxide (TiO₂) nanoparticles constitute the cornerstone of electron transport layers in state-of-the-art regular (n-i-p) perovskite solar cells, playing an important role in charge extraction kinetics and the crystallization of the perovskite absorber. However, their inherent limitations, such as insufficient electron mobility and high trap state density, hinder further improvements in device performance. This review presents a critical analysis of recent strategies aimed at engineering TiO₂ nanostructures for next-generation perovskite photovoltaics. We systematically evaluate advancements in preparation methods, elemental doping, and interfacial passivation aimed at modulating energy band alignment and suppressing non-radiative recombination. Furthermore, this review focuses on methods to alleviate current-voltage hysteresis and enhance photostability, as well as strategies for low-temperature synthesis applied to flexible substrates, providing future development directions for large-scale preparation.