Synthesis and characterization of stannic oxide thin films and their application in quantum dot sensitized solar cells

The thin films of Stannic Oxide (SnO₂) were deposited on fluorine-doped tin oxide substrates through ambient-modulated Chemical Bath Deposition (CBD). This was done by comparing air and oxygen-bubbled conditions to interpret oxygen's role in phase evolution and defect mitigation. Annealing transformed as deposited (tetragonal with orthorhombic traces) SnO phases into crystalline SnO₂ (mixed tetragonal-orthorhombic), as verified by X-ray diffraction revealing a structural shift. Optical analysis confirmed bandgap widening from ~ 2.0 eV to ~ 3.0 eV with high visible transmittance (> 85%), while scanning electron microscopy revealed granular morphologies influenced by deposition ambient. Quantum-dot-sensitized solar cells fabricated with PbS quantum dots (QDs) and polysulfide electrolyte attaining 0.316 % and 0.787 % power conversion efficiency with CuS and CuSe counter electrode under low-intensity illumination (15 mW cm⁻²). The low illumination intensity was deliberately chosen to evaluate device behavior under conditions relevant to indoor and low-light applications (an emerging direction for QDSSCs) and to minimize thermal stress and irreversible degradation of the polysulfide electrolyte and PbS layer. The work demonstrates a simple ambient-controlled CBD route for producing functional SnO₂ photoanodes and serves as cost-effective SnO₂-based QDSSCs; further interface engineering will be required to reach competitive efficiencies under full-sun conditions.