Al-doped TiO₂ nanocones as high-performance ETLs for eco-sustainable perovskite solar cells

Materials science plays a vital role in revolutionizing energy conversion systems with the manipulation of materials at atomic and molecular scales. The precision-engineered nanomaterials improve longevity, efficiency, and sustainability while mitigating the environmental footprints. Perovskite solar cells (PSCs) have thrived as a promising alternative to commercial solar cells, with the advantage of being economical and having easy processing techniques. We herein report the synthesis and characterization of titania nanocones with high transparency upon doping aluminum (2 wt%, 3 wt%, and 4 wt%) which acts as electron transport material in PSC. Nanocones act as photoactive material, as they interact with sunlight to transport electrons to the respective electrode. The examination of phase, crystallinity, morphology, opto-electronic properties, photovoltaic parameters, and the cell's efficiency were characterized by XRD, SEM, EDX, UV-DRS, BET analysis, field-dependent dark and photoconductivity analysis, and J-V analysis. In comparison with pure titania nanocones, Al-doped nanocones had increased length of nanocones reaching up to ~ 676 nm and exhibited a significant increase in conduction and collection of charges. The specific surface area increased up to 3 wt% of the dopant concentration (TA3) around 85.162 m²/g and dropped down further to 78.310 m²/g. The photoconductivity measurements showed that the doped sample with 3 wt% of aluminum (TA3) had a two-fold increase in photocurrent and the absorption edges had a shift towards the shorter wavelength from 316 to 300 nm in the ultraviolet spectrum, with narrowing of the bandgap. Thus, the doped sample with 3 wt% of aluminum with short-circuit current density (J_SC) ~ 34 mA/cm², open-circuit voltage (V_OC) ~ 950 mV, fill-factor (FF) ~ 0.856, and efficiency around 2.6% was ascertained to be a remarkable electron transport material (ETM) in this perovskite module.