Titanium dioxide (TiO 2 ) in the form of pellets (pressed powder) and thin films are investigated, revealing the presence of distinct phases: mainly anatase and rutile. Characterization of optical, structural and electrical properties were carried out on samples submitted to different sort of thermal annealing (TA), at distinct temperatures, 500 and 1000 o C, due to their influence on the obtained phases. TA temperature along with pressure application for sample conformation, determine the bands present in the photoluminescence (PL) spectra, being about 550nm, characteristic of anatase phase and 800nm, related to the presence of rutile phase. The bandgap of thin films is determined from optical absorbance data, yielding 3.4eV for anatase phase (indirect transition), and 2.9eV for rutile phase (direct transition). Besides, irradiation with monochromatic light strongly affects the thin film conductivity, but the energy range (above or below the bandgap energy) does not seem to affect the behavior, which is associated with the excitation of intrabandgap states or crystallites belonging to phases with distinct bandgaps.

<p>Two different methods are used to deposit Nb2O5 as compact electron transport layers in n-i-p double cation mixed-halide perovskite Cs0.17FA0.83Pb(I0.83Br0.17)3 solar cells; reactive sputtering and spin coating. These different Nb2O5 films influenced perovskite growth and the charge transport in the cells. Photovoltaic parameters were obtained with an average PCE of 17.0 % and 15.7% for the devices based on sputtered and spin-coated Nb2O5, respectively. The mobility and the extracted charges were higher in sputtered Nb2O5-based devices than in the spin-coated ones. This effect is attributed to the larger grain sizes observed in the perovskite films when deposited onto the sputtered Nb2O5 layers. The higher densities of grain boundaries in the spin-coated Nb2O5-based devices increase ion diffusion and are expected to decrease efficiency.