Improvement of absorption properties of TiO2 nanotubes by using CH3NH3PbBr3 perovskite as photosensitizer

Organic-inorganic perovskites have attracted much attention from researchers due to their high absorption in the visible part of the spectrum and low-cost fabrication. After absorption of the light, electron-hole pairs are formed. To separate electron-hole pairs and reduce recombination, perovskite is combined with TiO2 which has as a consequence, a spontaneous transition of electrons from perovskite to TiO2. This research aims to increase the contact surface of perovskite and TiO2 nanotubes by filling the nanotubes with perovskite material. The solution of methylammonium lead bromide perovskite (CH3NH3PbBr3) in dimethylformamide (DMF) was deposited on anodically synthesized TiO2 nanotubes by the high vacuum system and inert gas. The procedure involved degassation of the sample under high vacuum for 3 h at 200 °C, cooling of the sample, and putting the solution of CH3NH3PbBr3 in DMF, after which it was treated with inert gas (N2), as an overpressure which enabled the filling of the nanotubes with perovskite material. The diffuse reflectance spectroscopy measurement of the sample proved that deposition of CH3NH3PbBr3 improves the absorption properties of TiO2 nanotubes. The I-V characteristics of the sample showed photodiode behavior and characteristic hysteresis curve for perovskite material. The value of current under visible light for the sample without preconditioning was 46 mA, while after preconditioning value of current was 76 mA. The results indicate that a perovskite photodiode with increased contact between TiO2 and perovskite was made, which is the basis for future solar cell construction.