| 1. |
- Huang, Jing, et al.
(författare)
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Improved Performance of Colloidal CdSe Quantum Dot-Sensitized Solar Cells by Hybrid Passivation
- 2014
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 6:21, s. 18808-18815
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid passivation strategy is employed to modify the surface of colloidal CdSe quantum dots (QDs) for quantum dot-sensitized solar cells (QDSCs), by using mercaptopropionic acid (MPA) and iodide anions through a ligand exchange reaction in solution. This is found to be an effective way to improve the performance of QDSCs based on colloidal QDs. The results show that MPA can increase the coverage of the QDs on TiO2 electrodes and facilitate the hole extraction from the photoxidized QDs, and simultaneously, that the iodide anions can remedy the surface defects of the CdSe QDs and thus reduce the recombination loss in the device. This hybrid passivation treatment leads to a significant enhancement of the power conversion efficiency of the QDSCs by 41%. Furthermore, an optimal ratio of iodide ions to MPA was determined for favorable hybrid passivation; results show that excessive iodine anions are detrimental to the loading of the QDs. This study demonstrates that the improvement in QDSC performance can be realized by using a combination of different functional ligands to passivate the QDs, and that ligand exchange in solution effective approach to introduce can be an different ligands.
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| 2. |
- Jamshidi, Asgar, et al.
(författare)
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Efficiency Enhanced Colloidal Mn-Doped Type II Core/Shell ZnSe/CdS Quantum Dot Sensitized Hybrid Solar Cells
- 2015
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Ingår i: Journal of Nanomaterials. - : Hindawi Publishing Corporation. - 1687-4110 .- 1687-4129.
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal Mn-doped ZnSe/CdS core/shell quantum dots (QDs) are synthesized for the first time and employed as a strategy to boost the power conversion efficiency of quantum dot sensitized solar cells. By using Mn-doping as a band gap engineering tool for core/shell QDs an effective improvement of absorption spectra could be obtained. The mid-states generated by a proper Mn content alleviate carrier separation and enhance the electron injection rate, thus facilitating electron transport to the TiO2 substrate. It is demonstrated that a device constructed with 0.25% Mn-doped ZnSe/CdS leads to an enhancement of the electron injection rate and power conversion efficiency by 4 times and 1.3, respectively.
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| 3. |
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| 4. |
- Ning, Zhijun, et al.
(författare)
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Quantum rod-sensitized solar cells
- 2011
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 4:12, s. 1741-1744
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Tidskriftsartikel (refereegranskat)abstract
- An electron injection highway: CdSe nanorods with CdS seed material were applied to a quantum rod-sensitized TiO 2 solar cell that showed a higher electron injection efficiency than analogous quantum dot-sensitized solar cells: reducing the nanocrystals carrier confinement dimensions can improve electron injection efficiency of nanocrystal-sensitized solar cells.
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| 5. |
- Ning, Zhijun, et al.
(författare)
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Solar cells sensitized with type-II ZnSe-CdS core/shell colloidal quantum dots
- 2011
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 47:5, s. 1536-1538
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Tidskriftsartikel (refereegranskat)abstract
- Type-II quantum dots (QDs) were applied for QDs-sensitized solar cells for the first time and showed prominent absorbed photon to current conversion efficiency.
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| 6. |
- Ning, Zhijun, et al.
(författare)
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Type-II colloidal quantum dot sensitized solar cells with a thiourea based organic redox couple.
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:13, s. 6032-6037
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, one kind of org. electrolyte based on tetramethylthiourea is employed for quantum dot sensitized solar cells (QDSCs). By reducing the impedance between the electrolyte and the counter electrode, the fill factor of such org. electrolyte based QDSCs is significantly improved. It is possible to substantially increase the photovoltage and to reach an efficiency three times higher than that of a commonly used inorg. electrolyte. The light harvesting ability of the org. electrolyte based QDSCs is successfully extended by using type-II QDs, where the adsorption of ZnS gives an addnl. advantage in further enhancing the stability of the cells. It is obsd. that core/shell ZnSe/CdS type-II QDs give higher electron injection than CdS/ZnSe QDs, proving that the electron distribution in the QDs is important for the electron extn. A full working mechanism of the org. redox couple for the QDSCs is proposed. [on SciFinder(R)]
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| 7. |
- Teng, Chao, et al.
(författare)
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Two Novel Carbazole Dyes for Dye-Sensitized Solar Cells with Open-Circuit Voltages up to 1 V Based on Br-/Br3- Electrolytes.
- 2009
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 11:23, s. 5542-5545
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized solar cells (DSCs) based on two novel carbazole dyes and a Br-/Br3- redox mediator in dry CH3CN solns. as electrolytes yielded a Voc of 1.156 V and a η value of 3.68% and a Voc of 0.939 V and a η value of 5.22% under simulated AM 1.5, resp. The dyes have more pos. HOMO levels (1.59 and 1.38 V vs NHE) than the redox potential of Br-/Br3--based electrolytes, which have sufficient driving force to regenerate dyes. Under similar conditions with an I-/I3- instead of a Br-/Br3- redox mediator, DSCs sensitized by the dyes produced a Voc of 0.696 V and a η value of 2.36% and a Voc of 0.621 V and a η value of 4.10%, resp. [on SciFinder(R)]
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| 8. |
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| 9. |
- Yuan, Chunze
(författare)
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Development of Nanoparticle Sensitized Solar Cells
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, I have been working with the development of nanoparticle sensitized solar cells. In the subarea of quantum dot sensitized solar cells (QDSCs), I have investigated type-II quantum dots (QDs), quantum rods (QRs) and alloy QDs, and developed novel redox couples as electrolytes. I have also proposed upconversion nanoparticles as energy relay materials for dye-sensitized solar cells (DSCs).Colloidal ZnSe/CdS type-II QDs were applied for QDSCs for the first time. The interesting features of those refer to that their photoelectrons and photoholes are located on the different parts of the dot, namely in the CdS shell and in the ZnSe core, respectively. That spatial separation between photoelectrons and photoholes can so effectively enhance the charge extraction efficiency, thus facilitating the electron injection, and also effectively expand the absorption spectrum. All these characteristics contribute to a high photon to current conversion efficiency. Furthermore, a comparison between the photovoltaic performance of ZnSe/CdS and CdS/ZnSe QDSCs shows that the electron distribution is important for the electron injection of the QDs.Colloidal CdS/CdSe QRs were applied to quantum rod-sensitized solar cells (QRSCs). They showed a higher electron injection efficiency than the analogous QDSCs. It is concluded that reduction of the carrier confinement dimensions of the nanoparticles can improve the electron injection efficiency of the nanoparticle sensitized solar cells.Two types of organic electrolytes based on the redox couples of McMT-/BMT (OS1) and TMTU/TMTU-TFO (OS2) were used for the QDSCs. By reducing the charge recombination between the electrolyte and the counter electrode, the fill factor and the photovoltage of these QDSCs were significantly improved, resulting in a higher efficiency for the studied solar cells than that with a commonly used inorganic electrolyte.Ternary-alloy PbxCd1-xS QDs used as photosensitizers for QDSCs were found to improve the photocurrent compared to the corresponding CdS and PbS QDs. By considering the effect of different ratios of Pb to Cd in thePbxCd1-xS QDs on the photovoltaic performance it was discovered that the photocurrent increases and the photovoltage decreases with the increase of the ratio in a certain range.Upconversion (UC) nanoparticles provide a strategy to develop panchromatic solar cells. Three types of UC nanoparticles employed by DSCs were confirmed to work as energy relay materials for effectively extending the light-harvesting spectrum to the near-infrared (NIR) region. They were also found to play a role as scattering centers to enhance the photovoltaic performance of the solar cells.
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| 10. |
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| 11. |
- Yuan, Chunze, et al.
(författare)
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Improving the Photocurrent in Quantum-Dot-Sensitized Solar Cells by Employing Alloy PbxCd1-xS Quantum Dots as Photosensitizers
- 2016
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 6:6
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Tidskriftsartikel (refereegranskat)abstract
- Ternary alloy PbxCd1-xS quantum dots (QDs) were explored as photosensitizers for quantum-dot-sensitized solar cells (QDSCs). Alloy PbxCd1-xS QDs (Pb0.54Cd0.46S, Pb0.31Cd0.69S, and Pb0.24Cd0.76S) were found to substantially improve the photocurrent of the solar cells compared to the single CdS or PbS QDs. Moreover, it was found that the photocurrent increases and the photovoltage decreases when the ratio of Pb in PbxCd1-xS is increased. Without surface protecting layer deposition, the highest short-circuit current density reaches 20 mA/cm(2) under simulated AM 1.5 illumination (100 mW/cm(2)). After an additional CdS coating layer was deposited onto the PbxCd1-xS electrode, the photovoltaic performance further improved, with a photocurrent of 22.6 mA/cm(2) and an efficiency of 3.2%.
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| 12. |
- Yuan, Chunze, et al.
(författare)
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Simultaneous Multiple Wavelength Upconversion in a Core-Shell Nanoparticle for Enhanced Near Infrared Light Harvesting in a Dye-Sensitized Solar Cell
- 2014
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 6:20, s. 18018-18025
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of most photovoltaic devices is severely limited by near-infrared (NIR) transmission losses. To alleviate this limitation, a new type of colloidal upconversion nanoparticles (UCNPs), hexagonal core-shell-structured beta-NaYbF4:Er3+(2%)/NaYF4:Nd3+(30%), is developed and explored in this work as an NIR energy relay material for dye-sensitized solar cells (DSSCs). These UCNPs are able to harvest light energy in multiple NIR regions, and subsequently convert the absorbed energy into visible light where the DSSCs strongly absorb. The NIR-insensitive DSSCs show compelling photocurrent increases through binary upconversion under NIR light illumination either at 785 or 980 nm, substantiating efficient energy relay by these UCNPs. The overall conversion efficiency of the DSSCs was improved with the introduction of UCNPs under simulated AM 1.5 solar irradiation.
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| 13. |
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| 14. |
- Yuan, Chunze, 1979-
(författare)
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The Study of II-VI Semiconductor Nanocrystals Sensitized Solar Cells
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Semiconductor nanocrystals, also referred to as quantum dots (QDs), have been the focus of great scientific and technological efforts in solar cells, as a result of their advantages of low-cost, photostability, high molar extinction coefficients and size-dependent optical properties. Due to the multi-electron generation effect, the theoretically maximum efficiency of quantum dots-sensitized solar cells (QDSCs) is as high as 44%, which is much higher than that of dye-sensitized solar cells (DSCs). Thus QDSCs have a clear potential to overtake the efficiency of all other kinds of solar cells. In recent years, the efficiency of QDSCs has been improved very quickly to around 5%. It is however still much lower than that of DSCs. The low efficiency is mostly caused by the high electron loss between electrolyte and electrodes and the lack of an efficient electrolyte. In this thesis, we have been working to enhance the performance of QDSCs with II-VI group nanocrystals by increasing the electron injection efficiency from QDs to TiO2 and developing new redox couples in electrolyte. To increase the electron injection, firstly, colloidal ZnSe/CdS type-II QDs were synthesized and applied for QDSCs for the first time, whose photoelectron and photohole are located on CdS shell and ZnSe core, respectively. The spatial separation between photoelectron and photohole can effectively enhance the charge extraction efficiency, facilitating electron injection, and also effectively expand the absorption spectrum. All these characteristics contribute to the high photon to current conversion efficiency. Furthermore, a comparison between the performances of ZnSe/CdS and CdS/ZnSe QDs shows that the electron distribution is important for the electron injection of the QDs in QDSCs. Secondly, colloidal CdS/CdSe quantum rods (QRs) were applied to a quantum rod-sensitized solar cell (QRSCs) that showed a higher electron injection efficiency than analogous QDSCs. It is concluded that reducing the carrier confinement dimensions of nanocrystals can improve electron injection efficiency of nanocrystal sensitized solar cells. In this thesis, two types of organic electrolytes based McMT-/BMT and TMTU/TMTU-TFO were used for QDSCs. By reducing the charge recombination between the electrolyte and counter electrode, fill factor (FF) of these QDSCs was significantly improved. At the same time, the photovoltages of the QDSCs were remarkably increased. As a result, the overall conversion efficiency of QDSCs based on the new electrolytes was much higher than that with a commonly used inorganic electrolyte. In addition, CdS QDSCs on NiO photoelectrode were studied which shows a n-type photovoltaic performance. This performance is attributed to the formation of a thin Cd metal film before CdS QDs formation on NiO. Since the CB edge of CdS sits between the Fermi level and the CB edge of Cd metal, a much strong electron transfer between Cd and CdS QD is obtained, resulting in the observed n-type photovoltaic performance of these CdS/NiO QDSCs.
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| 15. |
- Yuan, Chunze, et al.
(författare)
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Use of colloidal upconversion nanocrystals for energy relay solar cell light harvesting in the near-infrared region
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:33, s. 16709-16713
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal upconversion (UC) nanocrystals were explored as energy relay materials for dye-sensitized solar cells for the first time. The utilization of colloidal UC nanocrystals was found to significantly enhance the upconversion efficiency and improve the photocurrent of the cells for low infrared irradiation intensity. In addition, it was found that UC nanocrystals of small size favor infiltration into a TiO2 film and bring higher relay efficiency. Finally, we found that UC nanocrystals can serve as a scattering material to increase the light absorption capability of the cells and increase the overall photocurrent of the cells under simulated sunlight irradiation.
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