A critical review on advancement and challenges in using TiO2 as electron transport layer for perovskite solar cell

Owing to its excellent optoelectronic properties along with good adhesion with the glass substrates and long-term stability, titanium dioxide has been intensively employed as a charge transport layer in perovskite-based solar cells (PSCs). In this review, we present a comprehensive summary of the recent progress in the synthesis and applications of titanium dioxides (TiO2) as an electron transport layer (ETL) in perovskite solar cells. The review initially introduces the basics of perovskite solar cells, including their working principles and applied configurations as well. The review then delves into a comprehensive discussion about the role and requirements of ETL in PSCs, such as long-term stability and high performance, as well as the electron transport mechanism in conventional and inverted planar PSCs. Thereafter, various TiO2 deposition processes are reviewed in detail, along with their benefits and drawbacks. Following that, we go over a synopsis of recent research on mesoporous, thick and thin layer-based TiO2 ETLs utilized in PSCs. Finally, this review provides a thorough overview of the current state-of-the-art research in TiO2-based ETLs for PSCs, as well as a discussion of the challenges and opportunities in this field. Overall, this review provides valuable insights into the synthesis and characterization of TiO2 nanomaterials used as ETLs, which may be utilized to drive the design and development of high-performance PSCs.