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Title: Study on dynamics of photoexcited charge injection and trapping in CdS quantum dots sensitized TiO{sub 2} nanowire array film electrodes

Abstract

The photoexcited electrons transfer dynamics of the CdS quantum dots (QDs) deposited in TiO{sub 2} nanowire array films are studied using surface photovoltage (SPV) and transient photovoltage (TPV) techniques. By comparing the SPV results with different thicknesses of QDs layers, we can separate the dynamic characteristics of photoexcited electrons injection and trapping. It is found that the TPV signals of photoexcited electrons trapped in the CdS QDs occur at timescales of about 2 × 10{sup −8} s, which is faster than that of the photoexcited electrons injected from CdS into TiO{sub 2}. More than 90 nm of the thickness of the CdS QDs layer will seriously affect the photoexcited electrons transfer and injection.

Authors:
; ; ; ; ;  [1]
  1. Key Laboratory for Special Functional Materials of Ministry of Education, Henan University, Kaifeng 475004, Henan (China)
Publication Date:
OSTI Identifier:
22300213
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 104; Journal Issue: 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; CADMIUM SULFIDES; ELECTRODES; ELECTRON BEAM INJECTION; ELECTRON TRANSFER; FILMS; INJECTION; LAYERS; PHOTOCURRENTS; PHOTOEMISSION; QUANTUM DOTS; THICKNESS; TITANIUM OXIDES; TRANSIENTS; TRAPPING; NANOWIRES

Citation Formats

Pang, Shan, Cheng, Ke, Yuan, Zhanqiang, Xu, Suyun, Cheng, Gang, and Du, Zuliang, E-mail: zld@henu.edu.cn. Study on dynamics of photoexcited charge injection and trapping in CdS quantum dots sensitized TiO{sub 2} nanowire array film electrodes. United States: N. p., 2014. Web. doi:10.1063/1.4879027.
Pang, Shan, Cheng, Ke, Yuan, Zhanqiang, Xu, Suyun, Cheng, Gang, & Du, Zuliang, E-mail: zld@henu.edu.cn. Study on dynamics of photoexcited charge injection and trapping in CdS quantum dots sensitized TiO{sub 2} nanowire array film electrodes. United States. doi:10.1063/1.4879027.
Pang, Shan, Cheng, Ke, Yuan, Zhanqiang, Xu, Suyun, Cheng, Gang, and Du, Zuliang, E-mail: zld@henu.edu.cn. Mon . "Study on dynamics of photoexcited charge injection and trapping in CdS quantum dots sensitized TiO{sub 2} nanowire array film electrodes". United States. doi:10.1063/1.4879027.
@article{osti_22300213,
title = {Study on dynamics of photoexcited charge injection and trapping in CdS quantum dots sensitized TiO{sub 2} nanowire array film electrodes},
author = {Pang, Shan and Cheng, Ke and Yuan, Zhanqiang and Xu, Suyun and Cheng, Gang and Du, Zuliang, E-mail: zld@henu.edu.cn},
abstractNote = {The photoexcited electrons transfer dynamics of the CdS quantum dots (QDs) deposited in TiO{sub 2} nanowire array films are studied using surface photovoltage (SPV) and transient photovoltage (TPV) techniques. By comparing the SPV results with different thicknesses of QDs layers, we can separate the dynamic characteristics of photoexcited electrons injection and trapping. It is found that the TPV signals of photoexcited electrons trapped in the CdS QDs occur at timescales of about 2 × 10{sup −8} s, which is faster than that of the photoexcited electrons injected from CdS into TiO{sub 2}. More than 90 nm of the thickness of the CdS QDs layer will seriously affect the photoexcited electrons transfer and injection.},
doi = {10.1063/1.4879027},
journal = {Applied Physics Letters},
number = 20,
volume = 104,
place = {United States},
year = {Mon May 19 00:00:00 EDT 2014},
month = {Mon May 19 00:00:00 EDT 2014}
}
  • Graphical abstract: - Highlights: • TiO{sub 2} film electrodes have been successfully sensitized with CdS QDs. • DSSC based on CdS QDs-sensitized TiO{sub 2} film with 4 min has the highest efficiency. • CdS QDs can improve the electron transport and reduce the electron recombination. • Our work open up a new avenue for the development of DSSCs. - Abstract: The TiO{sub 2} film electrodes sensitized with CdS quantum dots (QDs) via chemical bath deposition method were successfully prepared as the photoanode of dye-sensitized solar cells (DSSCs). Microstructural characterizations by XRD, SEM, TEM and EDX show that the CdS nanocrystalsmore » with the cubic structure have intimate contact to the TiO{sub 2} films. The amount of CdS QDs can be controlled by varying the dipping time. The experiment results demonstrate that the CdS QDs-sensitized solar cells show a wider absorption in the solar spectrum and an enhanced surface photovoltage response. The maximal photoelectric conversion efficiency of 5.57% was achieved by the DSSC based on CdS QDs-sensitized TiO{sub 2} film with 4 min. The performance improvement is ascribed to the enhancement of electron transport, the reduction of electron recombination and the long electron lifetime.« less
  • Graphical abstract: The changed SPV with chopping frequencies indicate the separation speeds of photogenerated charge carriers in different films. - Highlights: • Ag{sub 2}S-sensitized TiO{sub 2} films show good photoelectric responses in visible-light region. • Frequency-modulated SPV give dynamic information and evidence of Ag{sub 2}S QDSSCs’ performance. • Frequency-modulated SPV can supply complementary information in the study of Ag{sub 2}S ODSSCs. - Abstract: Ag{sub 2}S quantum-dots-sensitized TiO{sub 2} films with different amount of Ag{sub 2}S were fabricated by a successive ionic layer adsorption and reaction (SILAR) method. The separation and transport of photogenerated charge carriers at different spectral regions weremore » studied by the frequency-modulated surface photovoltage technology. Some novel dynamic information of photogenerated charge carriers in a wide spectral range is found. The results indicate that the rate and direction of separation (diffusion) for photogenerated charge carriers are closely related to the performance of quantum-dots-sensitized solar cells (QDSSCs) based on the Ag{sub 2}S/TiO{sub 2} nano-structure.« less
  • Dye-sensitized nanostructured TiO{sub 2} is a promising material for solar cell applications since it is expected to be produced at a relatively low cost and can give efficiencies of up to 10%. The charge transport in dye-sensitized nanostructured TiO{sub 2} was studied by laser pulse induced photocurrent transients. The experimental curves were compared to simulations using a diffusion model with an initial electron distribution of an exponential decay. The simulations were optimized with respect to the experimental curves giving an apparent diffusion coefficient of 6 {times} 10{sup {minus}6} cm{sup 2}/s for the electrons with an electrolyte of 0.1 M KImore » in propylene carbonate, the potential being +300 mV vs Ag/AgCl in ethanol. The charge transport was highly dependent on electrolyte composition and light intensity.« less
  • TiO{sub 2} branched nanostructures could be efficient as photoanodes for quantum dot-sensitized solar cells (QDSCs) due to their large surface area for QD deposition. In this study, Mn-doped CdS/Mn-doped CdSe deposited branched TiO{sub 2} nanorods were fabricated to enhance the photovoltaic performance of QDSCs. Mn doping in CdS and CdSe retards the recombination losses of electrons, while branched TiO{sub 2} nanorods facilitate effective electron transport and compensate for the low surface area of the nanorod structure. As a result, the charge-transfer resistance (R{sub CT}), electron lifetime (τ{sub e}), and the amount of QD deposition were significantly improved with branched TiO{submore » 2} nanorod based Mn-doped CdS/Mn-doped CdSe quantum dot-sensitized solar cell.« less