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Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method.

Sun H, Zhao P, Zhang F, Liu Y, Hao J - Nanoscale Res Lett (2015)

Bottom Line: The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared.The cycles of local deposition have great influence on their photoelectric properties.The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan, 250100, People's Republic of China.

ABSTRACT
Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor-Ag2S (0.9 eV) quantum dots (QDs)-in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

No MeSH data available.


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The schematic photovoltaic conversion of Ag2S/CdS/TNTs by SSM
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Fig9: The schematic photovoltaic conversion of Ag2S/CdS/TNTs by SSM

Mentions: In reference to the mechanism proposed in literatures [34–37], the schematic photovoltaic conversion of Ag2S/CdS/TNTs by SSM is shown in Fig. 9. The photogenerated electrons separate from the photogenerated holes under light irradiation. However, the photogenerated electrons and holes recombine with each other if the electrons cannot be transferred. The conduction band (CB) of the semiconductor (CdS) is located above the CB level of the TNTs, and the photogenerated electrons can transfer from the CB of the CdS to the CB of the adjacent TNTs. The electrons flow away through Ti substrate and wires rapidly. The valence band (VB) of the TNTs is below that of the adjacent CdS, the photogenerated holes transfer from the VB of the TNTs to that of the CdS, and the holes transfer to the surface of Ag2S/CdS/TNTs by SSM. The two factors can reduce the recombination probability of electrons and holes. The similar transfer process of the photogenerated electrons and holes of Ag2S and TNTS can happen. With a lower bandgap energy (0.9 eV), Ag2S has a wider range of light absorption, and photogenerated electrons and holes are easier to separate than wide-bandgap semiconductors, though they are ready to recombine at the same time, which can be reduced by the interaction between Ag2S, CdS and TiO2. However, the photogenerated electron numbers of Ag2S/CdS/TNTs via SILAR can be reduced because such a large amount of Ag2S uniformly deposited on the whole CdS/TNTs may reduce the light absorption of CdS and TNTs. Under irradiation, the photogenerated holes transferred to Ag2S and CdS, which will reduce the stability of Ag2S/CdS/TNTs by SSM in practical applications. So, 0.20 M Na2S and 0.20 M Na2SO3 aqueous solutions were used as electrolyte with sacrificial agent, and the holes in the Ag2S and CdS with active oxidation ability were captured by S2− and S2O32− in the electrolyte (2h+ + S2 − + SO32 − → S2O32 −) [38], which can enhance the stability of the Ag2S/CdS/TNTs by SSM.Fig. 9


Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method.

Sun H, Zhao P, Zhang F, Liu Y, Hao J - Nanoscale Res Lett (2015)

The schematic photovoltaic conversion of Ag2S/CdS/TNTs by SSM
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591224&req=5

Fig9: The schematic photovoltaic conversion of Ag2S/CdS/TNTs by SSM
Mentions: In reference to the mechanism proposed in literatures [34–37], the schematic photovoltaic conversion of Ag2S/CdS/TNTs by SSM is shown in Fig. 9. The photogenerated electrons separate from the photogenerated holes under light irradiation. However, the photogenerated electrons and holes recombine with each other if the electrons cannot be transferred. The conduction band (CB) of the semiconductor (CdS) is located above the CB level of the TNTs, and the photogenerated electrons can transfer from the CB of the CdS to the CB of the adjacent TNTs. The electrons flow away through Ti substrate and wires rapidly. The valence band (VB) of the TNTs is below that of the adjacent CdS, the photogenerated holes transfer from the VB of the TNTs to that of the CdS, and the holes transfer to the surface of Ag2S/CdS/TNTs by SSM. The two factors can reduce the recombination probability of electrons and holes. The similar transfer process of the photogenerated electrons and holes of Ag2S and TNTS can happen. With a lower bandgap energy (0.9 eV), Ag2S has a wider range of light absorption, and photogenerated electrons and holes are easier to separate than wide-bandgap semiconductors, though they are ready to recombine at the same time, which can be reduced by the interaction between Ag2S, CdS and TiO2. However, the photogenerated electron numbers of Ag2S/CdS/TNTs via SILAR can be reduced because such a large amount of Ag2S uniformly deposited on the whole CdS/TNTs may reduce the light absorption of CdS and TNTs. Under irradiation, the photogenerated holes transferred to Ag2S and CdS, which will reduce the stability of Ag2S/CdS/TNTs by SSM in practical applications. So, 0.20 M Na2S and 0.20 M Na2SO3 aqueous solutions were used as electrolyte with sacrificial agent, and the holes in the Ag2S and CdS with active oxidation ability were captured by S2− and S2O32− in the electrolyte (2h+ + S2 − + SO32 − → S2O32 −) [38], which can enhance the stability of the Ag2S/CdS/TNTs by SSM.Fig. 9

Bottom Line: The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared.The cycles of local deposition have great influence on their photoelectric properties.The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Colloid and Interface Chemistry & Key Laboratory of Special Aggregated Materials, Shandong University, Ministry of Education, Jinan, 250100, People's Republic of China.

ABSTRACT
Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor-Ag2S (0.9 eV) quantum dots (QDs)-in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

No MeSH data available.


Related in: MedlinePlus