TiO₂ nanotubes: An advanced electron transport material for enhancing the efficiency and stability of perovskite solar cells

Despite the preferential use of titanium dioxide (TiO₂) as electron transport layers (ETLs) for perovskite solar cells (PSCs), some problems are still needed to be solved to achieve better power conversion efficiency (PCE). Herein, TiO₂ nanotubes (TD-NTs) with network structures have been obtained through an inexpensive hydrothermal strategy. The obtained TD-NTs have been used in constructing PSCs as a favorable interface ETL. The PSC based on TD-NTs displayed a high PCE of 19.14%, increased by 11.4% compared to 17.18% for TiO₂ nanoparticles (TD-NPs) as a reference under the same conditions. The benefits beyond the amalgamation of nanotube structures are suppression of charge recombination and reinforcement of the transport pathways for carriers. The stability tests have shown that the cells with the TD-NT network maintain over 90% of their efficiency even after more than 500 h, much better than that of normal nanoparticle-based ones. Overall, TD-NT-ETL has demonstrated its potential in efficient and stable PSCs.