The parameter D eff was then calculated using the relation D eff = (R k/R w)(L 2/τ eff), where L is the thickness of the ZnO film (26 μm). The highest D eff value (8.05 × 10−3 cm2 s−1) was also obtained at the optimal dye adsorption time of 2 h. This high D eff value can be explained by more injected electrons and induced faster transport of electrons. The parameter L eff, calculated by the relation L eff = (D eff × τ eff)1/2, reflects the competition between the collection and recombination of electrons. A cell fabricated using the optimal dye adsorption time of 2 h achieved the highest

L eff value of BB-94 manufacturer 111.6 μm, which exceeds the thickness of the photoelectrode (26 μm). This indicates that most of the injected electrons reached the FTO substrate before recombination occurred. This L eff trend shows good agreement with that of J SC. Increased recombination can explain the significant drop in J SC values at other dye adsorption times. Overall, the EIS analysis results are in good agreement with the measured device performance parameters. The DSSC prepared using the optimized

fabrication condition (film thickness = 26 μm and dye adsorption time = 2 h) was also subjected to a long-term at-rest stability test, in which the cell was stored in the dark at room temperature. Figure 7 shows the changes in photovoltaic characteristics over time. The efficiency data shown in this figure are the average of three measurements. During the first 100 h, the device performance improved slightly. The power conversion efficiency increased from 4.76% JQEZ5 mouse to 5.61%, whereas J SC rose from 10.9 to 11.78 mA/cm2. From 100 to 3000 h, the overall conversion efficiency gradually decreased to 3.39% because of the decline of J SC, V OC, and FF. Thereafter, the overall conversion efficiency remained nearly unchanged for 8,000 h, as did the J SC, Thiamet G V OC, and FF values. Although the fabricated cell used a liquid Dibutyryl-cAMP molecular weight electrolyte, it demonstrated excellent at-rest stability and retained approximately 70% of its initial efficiency after more than 1 year of storage. Figure 7 At-rest stability of the

best-performing cell. The cell was prepared with a 26-μm film sensitized in a dye solution for 2 h. Conclusions In summary, this study reports the successful fabrication of DSSC photoelectrodes using commercially available ZnO particles sensitized with acidic N719 dye. The effects of two fabrication factors, the film thickness and the dye adsorption time, were systematically investigated. The results show that to obtain efficient ZnO/N719-based DSSCs, the dye adsorption time must be varied with the photoanode thickness. This is because the dye adsorption time suited for a particular film thickness does not apply to other film thicknesses. This is primarily because prolonged dye sensitization times lead to significant deterioration in the performance of ZnO-based cells.