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Chin. Phys. B, 2018, Vol. 27(6): 067305    DOI: 10.1088/1674-1056/27/6/067305

Enhanced transient photovoltaic characteristics of core-shell ZnSe/ZnS/L-Cys quantum-dot-sensitized TiO2 thin-film

Kui-Ying Li(李葵英), Lun Ren(任伦), Tong-De Shen(沈同德)
State Key Laboratory of Metastable Materials Science & Technology, Yanshan University, Qinhuangdao 066004, China
Abstract  Photoanodic properties greatly determine the overall performance of quantum-dot-sensitized solar cells (QDSCs). In the present report, the microdynamic behaviors of carriers in the nanocomposite thin-film, a ZnSe QD-sensitized mesoporous La-doped nano-TiO2 thin-film, as a potential candidate for photoanode, are probed via nanosecond transient photovoltaic (TPV) spectroscopy. The results confirm that the L-Cys ligand has a dual function serving as a stabilizer and molecular linker. Large quantities of interface states are located at the energy level with a photoelectric threshold of 1.58 eV and a quantum well (QW) depth of 0.67 eV. This QW depth is approximately 0.14 eV deeper than the depth of QW buried in the ZnSe QDs, and a deeper QW results in a higher quantum confinement energy. A strong quantum confinement effect of the interface state may be responsible for the excellent TPV characteristics of the photoanode. For example, the peak intensity of the TPV response of the QD-sensitized thin-film lasts a long time, from 9.40×10-7 s to 2.96×10-4 s, and the end time of the PTV response of the QD-sensitized thin-film is extended by approximately an order of magnitude compared with those of the TiO2 substrate and the QDs. The TPV characteristics of the QD-sensitized thin-film change from p-type to n-type for the QDs before and after sensitizing. These properties strongly depend on the extended diffusion length of the photogenerated carries and the reduced recombination rate of photogenerated electron-hole pairs, resulting in prolonged carrier lifetime and an increased level of electron injection into the TiO2 thin-film substrate.
Keywords:  sensitization      core-shell ZnSe quantum dots      mesoporous TiO2 thin-film      time-resolution photovoltage  
Received:  19 December 2017      Revised:  04 April 2018      Published:  05 June 2018
PACS:  73.63.-b (Electronic transport in nanoscale materials and structures)  
  78.20.-e (Optical properties of bulk materials and thin films)  
  73.63.Kv (Quantum dots)  
  78.56.-a (Photoconduction and photovoltaic effects)  
Fund: Project supported by the Natural Science Foundation of Hebei Province,China (Grant Nos.E2013203296 and E2017203029).
Corresponding Authors:  Kui-Ying Li     E-mail:

Cite this article: 

Kui-Ying Li(李葵英), Lun Ren(任伦), Tong-De Shen(沈同德) Enhanced transient photovoltaic characteristics of core-shell ZnSe/ZnS/L-Cys quantum-dot-sensitized TiO2 thin-film 2018 Chin. Phys. B 27 067305

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