Synthesis of a nanostructured rutile TiO2 electron transporting layer via an etching process for efficient perovskite solar cells: impact of the structural and crystalline properties of TiO2

In the present investigation, hollow and split nanostructures of rutile TiO2 have been synthesized using simple hydrothermal and chemical etching processes. Two typical structures such as TiO2 nanorods and nanoflowers were used as electron transporting layers (ETLs) for perovskite solar cells (PSCs). The optimized nanostructured ETLs were then used for mixed halide PSCs such as methyl ammonium iodide (MAPbI(3)), methyl ammonium iodide/chloride mixed-halide perovskite (MAPbI(3-x)Cl(x)) and (FAPbI(3))(0.85)(MAPbBr(3))(0.15) (herein FAPbI(3) = formamidinium lead halide and MAPbBr(3) = methylammonium lead bromide). The optimized results show a eta = 15.87% efficiency (J(SC) = 20.75 mA cm(-2), V-OC = 1.034, FF = 0.74) and a eta = 17.55% efficiency (J(SC) = 21.72 mA cm(-2), V-OC = 1.073, FF = 0.76) for (MAPbI(3-x)Cl(x)) and (FAPbI(3))(0.85)(MAPbBr(3))(0.15), respectively, for etched TiO2 with a split structure.