In this study, the TiO2 NP thin film is compressed before heat treatment. The procedure enhances the interconnection between the NPs, hence decreases the recombination probability. The performance of the DSSCs is improved. Besides, a thick photoanode induces a large surface area enhancing dye molecules to adsorb on it. Hence, a thick photoanode captures more light to generate photoexcited

electrons. However, the J SC requires that these electrons successfully transport to the FTO substrate (electrode) without recombination at the dye/photoanode or photoanode/electrolyte interfaces; therefore, electron diffusion length is also a key point that needs to be considered. Though a thick photoanode enhances the generation of photoexcited electrons, a long electron diffusion length is inevitable for Selleckchem CB-839 those photoexcited electrons generated in the deep layer. Thus, the J SC is a compromise between the two conflict factors: enlarged Selleck CAL-101 surface area by increasing photoanode thickness and increased thickness resulting in a long electron diffusion length. The experimental results indicate that the optimized thickness is 26.6 nm. The probability of recombination of injected electrons and the iodides in the electrolyte is smallest in this case. Therefore, sample D has the highest photo-to-electron conversion efficiency of 9.01%. The results also agree with those of

EIS and IPCE, as shown in the inset of Figure 6. Conclusions The effect of TiO2 NP photoanode thickness on the performance of the DSSC device was studied. The TiO2 NP photoanode thin film was fabricated by mechanical compression before thermal treatment. The final film was uniform and dense. The UV–vis spectrophotometer analysis indicates that the absorbance increases with the increase of the thickness of TiO2 NP thin film due to the large surface area enhancing the adsorption of dye molecules. However,

the optimal incident photon-to-current conversion efficiency and total energy conversion efficiencies were found in the TiO2 NP photoanode film with a thickness of 26.6 μm under an incident light intensity of 100 mW/cm2. The results indicate that there are two conflict factors acting together so that an optimal thickness is observed. The two factors are as follows: (1) Urocanase increasing the photoanode thickness could enlarge the surface area and enhance the adsorption of dye molecules which improves the light absorbance as well as the generation of photoexcited electrons and (2) a thick photoanode results in a long electron diffusion distance to the FTO substrate (electrode) which increases the probability of recombination and thus degrades the efficiencies. Acknowledgements This work was partially supported by the National Science Council of Taiwan, the Republic of China, and Core Facilities Laboratory in Kaohsiung-Pingtung area. References 1.