Vertically aligned TiO2 nanorod array as an electron transport layer in perovskite photodiode

Abstract

The development of metal oxide-based electron transport layers in perovskite solar cells (PSCs) is being intensively researched to achieve highly efficient PSCs. They offer the advantage of higher charge carrier mobility and stability compared to typical organic materials. To reduce the recombination of charge carriers, methylammonium lead bromide (MAPbBr3) perovskite was coupled with vertically aligned TiO2 nanorods (NRs) as an electron transport layer in this study. The TiO2 NRs were grown on commercial FTO glass in hydrothermal conditions. Titanium (IV) isopropoxide (TTIP) was added in drops, slowly, in the diluted solution of HCl. The obtained precursor solution was transferred into a Teflon-lined stainless steel autoclave which contained FTO substrates and heated at 150 °C for 2 h. Then, the substrates were cleaned using DI water and ethanol and annealed at 500 °C for 30 min. The solution of MAPbBr3 in dimethylformamide (DMF) was deposited on TiO2 NRs by spin coating technique. FESEM results showed that TiO2 NRs were porous and oriented vertically upwards to the substrate and that the perovskite material filled the space between TiO2 NRs. Diffuse reflectance spectroscopy measurement of the sample proved that the absorption edge of the prepared TiO2 NRs/MAPbBr3 was extended into the visible range. By measuring the I-V characteristics of the sample in the dark and under visible light, a hysteresis curve was obtained. Prepared TiO2 NRs/MAPbBr3 photodiode will be the basis for the construction of solar cells.