Sub-100 °C solution processed amorphous titania nanowire thin films for high-performance perovskite solar cells

• Amorphous titania nanowire thin films were prepared via a low temperature process.
• The titania evolved from nanoparticles to nanowires with increasing reaction time.
• Good titania coverage effectively blocked holes, suppressing charge recombination.
• PSCs based on ∼150 nm titania nanowire thin films yielded an efficiency of 14.67%.

The present work demonstrates a facile one-step process to fabricate thin films of amorphous titania nanowires on transparent conducting oxide substrates via hydrolysis of potassium titanium oxide oxalate in an aqueous solution at 90 °C. The resultant titania nanowire thin films (that have not undergone further annealing) are efficient electron transport layers in CH3NH3PbI3 perovskite solar cells, yielding full sun solar-to-electricity conversion efficiencies of up to 14.67% and a stabilized efficiency of 14.00% under AM 1.5G one sun illumination, comparable to high temperature sintered TiO2 counterparts. The high photovoltaic performance is attributed to the porous nanowire network that facilitates perovskite infiltration, its unique 1D geometry and excellent surface coverage for efficient electron transport, as well as suppressed charge recombination between FTO and perovskite.

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