| 1. |
- Leandri, Valentina, et al.
(författare)
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Excited-State Dynamics of [Ru(bpy)(3)](2+) Thin Films on Sensitized TiO2 and ZrO2
- 2019
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Ingår i: ChemPhysChem. - : Wiley-VCH Verlagsgesellschaft. - 1439-4235 .- 1439-7641. ; 20:4, s. 618-626
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Tidskriftsartikel (refereegranskat)abstract
- The excited state dynamics of Tris(2,2 '-bipyridine)ruthenium(II) hexafluorophosphate, [Ru(bpy)(3)(PF6)(2)], was investigated on the surface of bare and sensitized TiO2 and ZrO2 films. The organic dyes LEG4 and MKA253 were selected as sensitizers. A Stern-Volmer plot of LEG4-sensitized TiO2 substrates with a spin-coated [Ru(bpy)(3)(PF6)(2)] layer on top shows considerable quenching of the emission of the latter. Interestingly, time-resolved emission spectroscopy reveals the presence of a fast-decay time component (25 +/- 5 ns), which is absent when the anatase TiO2 semiconductor is replaced by ZrO2. It should be specified that the positive redox potential of the ruthenium complex prevents electron transfer from the [Ru(bpy)(3)(PF6)(2)] ground state into the oxidized sensitizer. Therefore, we speculate that the fast-decay time component observed stems from excited-state electron transfer from [Ru(bpy)(3)(PF6)(2)] to the oxidized sensitizer. Solid-state dye sensitized solar cells (ssDSSCs) employing MKA253 and LEG4 dyes, with [Ru(bpy)(3)(PF6)(2)] as a hole-transporting material (HTM), exhibit 1.2 % and 1.1 % power conversion efficiency, respectively. This result illustrates the possibility of the hypothesized excited-state electron transfer.
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| 2. |
- Sadollahkhani, Azar, et al.
(författare)
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Energetic Barriers to Interfacial Charge Transfer and Ion Movement in Perovskite Solar Cells
- 2017
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Ingår i: ChemPhysChem. - : WILEY-V C H VERLAG GMBH. - 1439-4235 .- 1439-7641. ; 18:21, s. 3047-3055
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Tidskriftsartikel (refereegranskat)abstract
- Highly efficient perovskite solar cells have been characterized by current-density/voltage measurements in the dark at varied scan rates. The results were compared to the solar cells without a hole-transporting layer to investigate the role of ultrathin hole-transporting layers in solar-cell function. The parameters of internal voltage, diode ideality factor, capacitive current, and capacitance were calculated from the current-density/voltage response of the cells in the dark. The results show that the absence of the hole-transporting layer can cause a large recombination current within the depletion region at the gold contact/perovskite interface, and thus affects the cell performance.
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| 3. |
- Sadollahkhani, Azar, et al.
(författare)
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Photocatalytic properties of different morphologies of CuO for the degradation of Congo red organic dye
- 2014
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Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 40:7, s. 11311-11317
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Tidskriftsartikel (refereegranskat)abstract
- In this study, Congo red organic dye was degraded by different morphologies of CuO and it was found that CuO nanorods are more favorable for the degradation of Congo red due to their more specific surface area and sensitive surface for the Congo red. All the CuO nanostructures were prepared by low temperature aqueous growth method. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) techniques were used for the morphological and structural characterization of CuO nanostructures. The relative degradation of Congo red for nanorods, nanoleaves and nanosheets was in order 67%, 48% and 12% respectively.
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| 4. |
- Sadollahkhani, Azar, et al.
(författare)
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Synthesis, structural characterization and photocatalytic application of ZnO@ZnS core-shell nanoparticles
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 4:70, s. 36940-36950
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Tidskriftsartikel (refereegranskat)abstract
- ZnO nanoparticles were synthesized by co-precipitation with no capping agent followed by covering with ZnS using a solution-based chemical method at low temperature. By variation of the solution concentrations it was found that the fully-covering ZnS shell forms by a reaction of Na2S with ZnO NPs followed by the formation of ZnS nano-crystals by the reaction of Na2S with ZnCl2. The mechanism that led to full coverage of the ZnO core is proposed to be the addition of ZnCl2 at a later stage of the growth which guarantees a continuous supply of Zn ions to the core surface. Moreover, the ZnS nanocrystals that uniformly cover the ZnO NPs show no epitaxial relationship between the ZnO core and ZnS shell. The slow atomic mobility at the low reaction temperature is attributed to the non-epitaxial uniform ZnS shell growth. The rough surface of the ZnO grains provides initial nucleation positions for the growth of the ZnS shell nano-crystals. The low growth temperature also inhibits the abnormal growth of ZnS grains and results in the homogeneous coverage of ZnS nano-crystals on the ZnO core surface. The as-synthesized ZnO@ZnS core-shell nanoparticles were used as a photocatalyst to decompose Rose Bengal dye at three different pH values. ZnO@ZnS core-shell nanoparticles perform as a more active photocatalyst at a pH of 4, while pure ZnO nanoparticles are more efficient at a pH of 7.
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| 5. |
- Zhang, Wei, et al.
(författare)
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Investigation of Triphenylamine (TPA)-Based Metal Complexes and Their Application in Perovskite Solar Cells
- 2017
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 2:12, s. 9231-9240
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Tidskriftsartikel (refereegranskat)abstract
- Triphenylamine-based metal complexes were designed and synthesized via coordination to Ni(II), Cu(II), and Zn(II) using their respective acetate salts as the starting materials. The resulting metal complexes exhibit more negative energy levels (vs vacuum) as compared to 2,2', 7,7'-tetrakis(N, N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD), high hole extraction efficiency, but low hole mobilities and conductivities. Application of dopants typically used for Spiro-OMeTAD was not successful, indicating a more complicated mechanism of partial oxidation besides the redox potential. However, utilization as hole-transport material was successful, giving a highest efficiency of 11.1% under AM 1.5G solar illumination.
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| 6. |
- Zhang, Wei, et al.
(författare)
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Mechanistic Insights from Functional Group Exchange Surface Passivation : A Combined Theoretical and Experimental Study
- 2019
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Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 2:4, s. 2723-2733
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Tidskriftsartikel (refereegranskat)abstract
- Four different functional groups including amino (-NH2), phosphine (-PH2), hydroxyl (-OH), and thiol (-SH) were combined with POSS (polyhedral oligomeric silsesquioxane) molecules to investigate how functional groups affect the surface passivation of POSS systems. Results from density-functional theory (DFT) calculations indicate that functional group amino (-NH2) with adsorption energy 86 (56) kJ mol(-1) is consistently better than that of thiol (-SH) with adsorption energy 68 (43) kJ mor(-1) for different passivation mechanisms. Theoretical studies on the analogous POSS-OH and POSS-PH2 systems show similar adsorption energies. Two of the systems were also investigated experimentally; aminopropyl isobutyl POSS (POSS-NH2) and mercaptopropyl isobutyl POSS (POSS-SH) were applied as passivation materials for MAPbI(3) (MA = methylammonium) perovskite and (FA)(0.85)(MA)(0.15)Pb(I-3)(0.85)(Br-3)(0)(.15)(FA = formamidinium) perovskite films. The same conclusion was drawn based on the results from contact angle studies, X-ray diffraction (XRD), and the stability of solar cells in ambient atmosphere, indicating the vital importance of choice of functional groups for passivation of the perovskite materials.
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