Low temperature grown ZnO@TiO2 core shell nanorod arrays for dye sensitized solar cell application

•ZnO@TiO2 core shell nanorod has been grown on FTO substrate using low temperature solution method.•TEM, XRD, EDX results confirmed the existing of titana shell, uniformly covered rod's surface.•TiO2 shell suppressed recombination, demonstrated significant enhancement in cell's efficiency.•Core shell DSSC's efficiency achieved as high as 3.03%, 3 times higher than that of ZnO nanorods.

High aspect ratio ZnO nanorod arrays were synthesized on fluorine-doped tin oxide glasses via a low temperature solution method. By adjusting the growth condition and adding polyethylenimine, ZnO nanorod arrays with tunable length were successfully achieved. The ZnO@TiO2 core shells structures were realized by a fast growth method of immersion into a (NH4)2·TiF6 solution. Transmission electron microscopy, X-ray Diffraction and energy dispersive X-ray measurements all confirmed the existence of a titania shell uniformly covering the ZnO nanorod's surface. Results of solar cell testing showed that addition of a TiO2 shell to the ZnO nanorod significantly increased short circuit current (from 4.2 to 5.2 mA/cm2), open circuit voltage (from 0.6 V to 0.8 V) and fill factor (from 42.8% to 73.02%). The overall cell efficiency jumped from 1.1% for bare ZnO nanorod to 3.03% for a ZnO@TiO2 core shell structured solar cell with a 18–22 nm shell thickness, a nearly threefold increase.

Graphical abstractThe synthesis process of coating TiO2 shell onto ZnO nanorod core is shown schematically. A thin, uniform, and conformal shell had been grown on the surface of the ZnO core after immersing in the (NH4)2·TiF6 solution for 5–15 min.Figure optionsDownload full-size imageDownload as PowerPoint slide