Enhanced performance of planar perovskite solar cells using dip-coated TiO2 as electron transporting layer

Nanostructured titanium dioxide thin films (TiO2) have been deposited on indium tin oxide (ITO) substrate, using dip-coating process from partial hydrolysis and condensation of tetrabutylorthotitanate, and using butanol and acetic acid respectively as solvent and catalyst. The effect of film thickness on the microstructural, morphological and optical properties was investigated, as well as their applicability as electron transporting layer for planar perovskite solar cells (PSCs). In all cases, well-crystallized anatase TiO2 films with a relatively smooth and homogeneous surface were obtained, while the optical band-gap of the films showed a small increase from 3.25 eV to 3.4 eV by increasing the film thickness from 50 nm to 90 nm. On the other hand, the refractive index (n) tends towards a value of 2 above 400 nm, while the extinction coefficients (k) goes down to zero. In addition, these TiO2 films deposited on ITO/glass substrates were used as electron transporting layer in planar PSCs. Thus, the important role in electron transport obtained for TiO2, allowed to improve the performance of the device and indicated the potential of the dip-coated TiO2 as an electron transporting layer for planar PSCs.