Optimization FTO/c‐TiO ₂ Capped with m‐TiO ₂ Electron Transport Layer for Efficient Interfacial Charge Carriers’ Extraction and Transport Prepared by Spray Pyrolysis

This study explores the fabrication of compact‐titanium dioxide (c‐TiO 2 ) electron transport layer capped with mesoporous‐titanium dioxide (m‐TiO 2 ) using spray pyrolysis while controlling layer thickness. X‐ray diffraction confirmed a crystalline rutile c‐TiO 2 structure, with crystallite size increasing from 22 to 24 nm as deposition time increased. Field emission‐scanning electron microscopy showed uniform surface coverage, with average grain size increasing from 195.57 to 242.34 nm, and UV–vis spectra indicated a bandgap near 430 nm. Electrical measurements revealed improved conductivity (3 × 10 6 to 1.18 × 10 7 S/m) and reduced sheet resistance (7.34–6.33 Ω/□). The best conductivity was achieved with a 7 s meso ‐epitaxial TiO 2 layer, enhancing electron transport and charge carrier mobility. Current‐voltage (I–V) characteristics demonstrated enhanced electron transport properties, with increased charge carrier mobility from 1.059 × 10 3 to 2.523 × 10 3 cm 2 V −1 s −1 . Furthermore, electron‐only devices with meso ‐passivated TiO 2 showed a higher trap density (2.148 × 10 15 cm −3 ) but improved mobility (1.857 × 10 3 cm 2 V −1 s −1 ) compared to pristine TiO 2 . These findings highlight the potential of meso ‐epitaxial TiO 2 for enhancing inorganic perovskite solar cells.