Free standing TiO2 nanotube array electrodes with an ultra-thin Al2O3 barrier layer and TiCl4 surface modification for highly efficient dye sensitized solar cells

Abstract

Dye sensitized solar cells were fabricated with free standing TiO2 nanotube (TNT) array films, which were prepared by template assisted atomic layer deposition (ALD) with precise wall thickness control. Efforts to improve the photovoltaic performance were made by using Al2O3 barrier layer coating in conjunction with TiCl4 surface modification. An Al2O3 thin layer was deposited on the TNT electrode by ALD to serve as the charge recombination barrier, but it suffers from the drawback of decreasing the photoelectron injection from dye into TiO2 when the barrier layer became too thick. With the TiCl4 treatment in combination with optimal thickness coating, this problem could be avoided. The co-surface treated electrode presents superior surface property with low recombination rate and good electron transport property. A high conversion efficiency of 8.62% is obtained, which is about 1.8 times that of the device without surface modifications.

Alumina Coatings on Fluorine-Doped Tin Oxide@Titanium Dioxide as Photoanode for Dye-Sensitized Solar Cells

“…The charge transfer resistance R 2 of F-T, F-T-A, F-T-2A and F-T-3A is 23.05 Ω, 18.86 Ω, 17.88 Ω and 20.66 Ω respectively, as extracted from the Nyquist plots. The resistance R 2 of F-T-xA is small compared with 22.3 Ω for a similar photoanode structure constructed by TiO 2 nanotubes modified with TiCl 4 treatment in conjunction with an Al 2 O 3 barrier layer [31]. It illustrates that a more efficient transport is achieved in F-T than in TiO 2 nanotube film, namely a drift transport.…”

“…Another study by Liu et al prepared a thin Al 2 O 3 -sheathed 3-dimentional (3-D) fluorinated tin oxide (FTO) as photoanodes of DSCs,at the aid of drift transport at the FTO/Al 2 O 3 interfaces, an efficiency of 1.536% was obtained[7]. In addition, Gao et al received improved photovoltaic performance made by using Al 2 O 3 barrier layer coating on TiO 2 nanotubes in conjunction with TiCl 4 surface modification[31].…”

Self-organized Anodic TiO2 Nanotubes: Functionalities and Applications Due to a Secondary Material

“…However, recent report by Gao and coworkers shows synthesis of TiO 2 nanotubes with AR ≈ 200 nm, shown in Fig. 3.15c, using templating of PAA by ALD [71]. Moreover, they have shown, that an additional coating of Al 2 O 3 (shown in Fig.…”

“…Figure 3.15a, b shows selected examples of resulting nanotubular structures that were published in several reports [67][68][69][70][71]. Another approach-etch-back technique-was used recently to prepare low-aspect ratio titania nanotubes, but with extremely high degree of ordering [72].…”

“…ZnO, SnO 2 , WO 3 ) by using conventional ALD cycles (typically 5-6) using appropriate precursors into nanotubes with a tube diameter of 95 nm and the layer thickness of 7.5 μm (AR ≈ 80). In the [71] next turn, they have used a tailored reduction by using atomic hydrogen flow through the as-deposited nanotubes. Using this approach, they managed to obtain non-stoichometric suboxides strongly attached to tube walls.…”