High efficiency dye-sensitized solar cells based on multilayer stacked TiO2 nanoparticle/nanotube photoelectrodes

To investigate the photon-trapping effect and scattering layer effect of a TiO2 multilayer in dye-sensitized solar cells (DSSCs), we designed the most optimal electrode using a combined, nanoparticle TiO2 (TNP)/nanotube TiO2 (TNT) electrode array. The TNT had a width, wall thickness and inner pore diameter of about 7–9 nm, 1 nm and 6 nm, respectively. The multilayer's efficiency was higher than that of the monolayer in the photocurrent–voltage (I–V) curve. The efficiency of the cell, including the TNT scattering layer, was enhanced and the impedance of electrochemical impedance spectroscopy (EIS) was decreased. These results indicated that the light scattering layer of TNT had a longer electron transfer path and higher charge-collection efficiency. The short circle current was increased by approximately 12.6% and the incident photon-to-current conversion efficiency (IPCE) in the maximum peak was also enhanced by about 25%, compared to the DSSC assembled without the TNT scattering layer.

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► The multilayer's efficiency was higher than that of the monolayer in the photocurrent–voltage (I–V) curve.
► The impedance of electrochemical impedance spectroscopy (EIS) was decreased on the TNT-multilayered DSSC.
► The short circle current was increased by approximately 12.6% and the IPCE in the maximum peak was also enhanced by about 25% on the TNT-multilayered DSSC.