Luminescent europium-doped titania for efficiency and UV-stability enhancement of planar perovskite solar cells

Perovskite solar cells (PSCs) have demonstrated high power conversion efficiencies (PCEs) but poor stability against ultraviolet (UV) irradiation. Here, we report a one-pot synthesized luminescent europium-doped titania (Eu-TiO₂) via chemical-bath deposition at low-temperature (70 °C) for planar PSCs, which enables simultaneous efficiency and UV-stability enhancement. We show that the Eu-TiO₂ could effectively convert damaging UV photons into useful visible luminescence for additional light harvesting. A more optimal energy band alignment at the Eu-TiO₂/perovskite interface leads to facilitated charge extraction and suppressed non-radiative recombination. The use of Eu-TiO₂ in PSCs results in increased photocurrent and open-circuit voltage, yielding an enhanced PCE of 21.40% with relative to pristine TiO₂ device (19.22%). More importantly, the Eu-TiO₂ devices exhibit remarkably improved UV stability, retaining 75% of the initial PCE after exposing to UV illumination for 500 h, while the devices with pristine TiO₂ lost the majority of their original PCEs in 150 h. As a proof-of-concept, we further demonstrate the scalability of our method by fabricating a large-area Eu-TiO₂ film of 64 cm² showing excellent uniformity.