Laser processing of Li-doped mesoporous TiO₂ for ambient-processed mesoscopic perovskite solar cells

Mesoporous titanium dioxide (m-TiO₂) has gained significant attention in photocatalytic, photoelectrochemical, energy storage, and photovoltaic applications. However, the performance of m-TiO₂-based devices is often hindered by their poor electrical conductivity, low electron mobility, and high electronic trap density. Doping m-TiO₂ with alkali-metal elements is a promising method to tackle these issues. Herein, an ultrafast laser treatment is presented to introduce lithium (Li) doping into m-TiO₂ (Li-doped m-TiO₂) to enhance its charge transport ability for mesoscopic perovskite solar cells (PSCs). Remarkably, the laser treatment only needs 42 s irradiation in total at the highest temperature of 800-850 °C to prepare the Li-doped m-TiO₂, compared to the traditional furnace treatment at a temperature of 500 °C for 60 min. Consequently, PSCs assembled under high relative humidity (60-75%) using the laser treatment exhibited a power conversion efficiency (PCE) of 19.15%, higher than that of the furnace treatment of 18.10%. The improvement is due to the enhanced interconnection between the Li-doped m-TiO₂ nanoparticles, reduced oxygen vacancies, and improved interfacial contact at m-TiO₂/perovskite, resulting from the laser treatment. These factors contribute to an improved electron transport capability, reduced charge recombination, and suppressed hysteresis behaviour in the PSCs. The ultrafast laser treatment introduced here offers a novel path for rapid manufacturing of metal-doped m-TiO₂ materials for PSCs and other related applications.