Clean and flexible synthesis of TiO₂ nanocrystallites for dye-sensitized and perovskite solar cells

A clean and flexible synthesis of TiO₂ nanocrystallites for dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs) was proposed. Anatase nanocrystallites with different morphologies and sizes ranging from 5 nm to 30 nm were synthesized in one pot via the microwave solvothermal method using different types of alcohol solvents, namely, n-propanol (NPA), isopropanol (IPA), and octanol (OCT). No ionic additive was added during the synthesis. The influences of crystallite size and morphology on the photovoltaic performances of the DSSCs and PSCs were investigated. Results showed that using OCT (5–7 nm) as a photoanode offered the highest power conversion efficiency (PCE), which gave rise to the apparent high dye loading capability and long electron recombination lifetime of OCT. The best PCE of the OCT-based DSSC device reached 9.58%, with the film thickness being only 10.6 μm where no scattering layer was needed. By contrast, the IPA (20–30 nm)-based photoanode showed good adaptability to PSC applications because of its homogeneity and large mean pore size that facilitated the infiltration of the perovskite sensitizer. The IPA-based PSC device attained the highest PCE of 15.3%, with J_sc being 21.55 mA/cm² and V_OC being 1.07 V.