| 1. |
- Aitola, Kerttu, et al.
(författare)
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Carbon nanotube-based hybrid hole-transporting material and selective contact for high efficiency perovskite solar cells
- 2016
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 9:2, s. 461-466
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a high efficiency perovskite solar cell with a hybrid hole-transporting material-counter electrode based on a thin single-walled carbon nanotube (SWCNT) film and a drop-cast 2,2,7,-7-tetrakis(N, N-di-p-methoxyphenylamine)-9,90-spirobifluorene (Spiro-OMeTAD) hole-transporting material (HTM). The average efficiency of the solar cells was 13.6%, with the record cell yielding 15.5% efficiency. The efficiency of the reference solar cells with spin-coated Spiro-OMeTAD hole-transportingmaterials (HTMs) and an evaporated gold counter electrode was 17.7% (record 18.8%), that of the cells with only a SWCNT counter electrode (CE) without additional HTM was 9.1% (record 11%) and that of the cells with gold deposited directly on the perovskite layer was 5% (record 6.3%). Our results show that it is possible to manufacture high efficiency perovskite solar cells with thin film (thickness less than 1 mu m) completely carbon-based HTMCEs using industrially upscalable manufacturing methods, such as press-transferred CEs and drop-cast HTMs.
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| 2. |
- Aitola, Kerttu, et al.
(författare)
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Carbon nanotube film replacing silver in high-efficiency solid-state dye solar cells employing polymer hole conductor
- 2015
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Ingår i: Journal of Solid State Electrochemistry. - : Springer Science and Business Media LLC. - 1432-8488 .- 1433-0768. ; 19:10, s. 3139-3144
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Tidskriftsartikel (refereegranskat)abstract
- A semitransparent, flexible single-walled carbon nanotube (SWCNT) film was efficiently used in place of evaporated silver as the counter electrode of a poly(3,4-ethylenedioxythiophene) polymer-based solid-state dye solar cell (SSDSC): the solar-to-electrical energy conversion efficiency of the SWCNT-SSDSC was 4.8 % when it was 5.2 % for the Ag-SSDSC. The efficiency difference stemmed from a 0.1-V difference in the open-circuit voltage, whose reason was speculated to be related to the different recombination processes in the two types of SSDSCs.
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| 3. |
- Aitola, Kerttu, et al.
(författare)
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High Temperature-Stable Perovskite Solar Cell Based on Low-Cost Carbon Nanotube Hole Contact
- 2017
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Ingår i: Advanced Materials. - : Wiley-VCH Verlagsgesellschaft. - 0935-9648 .- 1521-4095. ; 29:17
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Tidskriftsartikel (refereegranskat)abstract
- Mixed ion perovskite solar cells (PSC) are manufactured with a metal-free hole contact based on press-transferred single-walled carbon nanotube (SWCNT) film infiltrated with 2,2,7,-7-tetrakis(N, N-di-p-methoxyphenylamine)-9,90-spirobifluorene (Spiro-OMeTAD). By means of maximum power point tracking, their stabilities are compared with those of standard PSCs employing spin-coated Spiro-OMeTAD and a thermally evaporated Au back contact, under full 1 sun illumination, at 60 degrees C, and in a N-2 atmosphere. During the 140 h experiment, the solar cells with the Au electrode experience a dramatic, irreversible efficiency loss, rendering them effectively nonoperational, whereas the SWCNT-contacted devices show only a small linear efficiency loss with an extrapolated lifetime of 580 h.
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| 4. |
- Aitola, Kerttu, et al.
(författare)
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Highly catalytic carbon nanotube counter electrode on plastic for dye solar cells utilizing cobalt-based redox mediator
- 2013
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 111, s. 206-209
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Tidskriftsartikel (refereegranskat)abstract
- A flexible, slightly transparent and metal-free random network of single-walled carbon nanotubes (SWCNTs) on plain polyethylene terephthalate (PET) plastic substrate outperformed platinum on conductive glass and on plastic as the counter electrode (CE) of a dye solar cell employing a Co(II/III)tris(2,2'-bipyridyl) complex redox mediator in 3-methoxypropionitrile solvent. The CE charge-transfer resistance of the SWCNT film was 0.60 Omega cm(2), 4.0 Omega cm(2) for sputtered platinum on indium tin oxide-PET substrate and 1.7 Omega cm(2) for thermally deposited Pt on fluorine-doped tin oxide glass, respectively. The solar cell efficiencies were in the same range, thus proving that an entirely carbon-based SWCNT film on plastic is as good CE candidate for the Co electrolyte. (C) 2013 Elsevier Ltd. All rights reserved.
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| 5. |
- Cappel, Ute B, et al.
(författare)
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Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells.
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:40, s. 34970-34978
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Tidskriftsartikel (refereegranskat)abstract
- ) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.
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| 6. |
- Cheng, Ming, et al.
(författare)
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Acceptor Donor Acceptor type ionic molecule materials for efficient perovskite solar cells and organic solar cells
- 2016
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 30, s. 387-397
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite solar cells (PSCs) have attracted significant interest and hole transporting materials (HTMs) play important roles in achieving high efficiency. Here, we report additive free ionic type HTMs that are based on 2-ethylhexyloxy substituted benzodithiophene (BDT) core unit. With the ionization of end-capping pyridine units, the hole mobility and conductivity of molecular materials are greatly improved. Applied in PSCs, ionic molecular material M7-TFSI exhibits the highest efficiency of 17.4% in the absence of additives [lithium bis(trifluor-omethanesulfonyl)imide and 4-tert-butylpyridine]. The high efficiency is attributed to a deep highest occupied molecular orbital (HOMO) energy level, high hole mobility and high conductivity of M7-TFSI. Moreover, due to the higher hydrophobicity of M7-TFSI, the corresponding PSCs showed better stability than that of Spiro-OMeTAD based ones. In addition, the strong absorption and suitable energy levels of materials (M6, M7-13r and M7-TFSI) also qualify them as donor materials in organic solar cells (OSCs) and the devices containing M7-TFSI as donor material displayed an efficiency of 6.9%.
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| 7. |
- Cheng, Ming, et al.
(författare)
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Highly Efficient Integrated Perovskite Solar Cells Containing a Small Molecule-PC70BM Bulk Heterojunction Layer with an Extended Photovoltaic Response Up to 900 nm
- 2016
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 28:23, s. 8631-8639
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a high efficiency perovskite solar cell (PSC) integrated with a bulk heterojunction layer, based on acceptor-donor-acceptor (A-D-A) type hole transport material (HTM) and PC70BM composite, yielding improved photoresponse. Two A-D-A-structured hole transporting materials termed M3 and M4 were designed and synthesized. Applied as HTMs in PSCs, power conversion efficiencies (PCEs) of 14.8% and 12.3% were obtained with M3 and M4, respectively. The HTMs M3 and M4 show competitive absorption, but do not contribute to photocurrent, resulting in low current density. This issue was solved by mixing the HTMs with PC70BM to form a bulk heterojunction (BHJ) layer and integrating this layer into the PSC as hole transport layer (HTL). Through careful interface optimization, the (FAPbI(3))(0.85)(MAPbBr(3))(0.15)/HTM:PC70BM integrated devices showed improved efficiencies of 16.2% and 15.0%, respectively. More importantly, the incident-photon-to-current conversion efficiency (IPCE) spectrum shows that the photoresponse is extended to 900 nm by integrating the M4:PC70BM based BHJ and (FAPbI(3))(0.85)(MAPbBr(3))(0.15) layers.
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| 8. |
- Hua, Yong, et al.
(författare)
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Facile synthesis of fluorene-based hole transport materials for highly efficient perovskite solar cells and solid-state dye-sensitized solar cells
- 2016
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 26, s. 108-113
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Tidskriftsartikel (refereegranskat)abstract
- Two novel low-cost fluorene-based hole transport materials (HTMs) HT1 and HT2 as alternatives to the expensive HTM Spiro-OMeTAD have been designed and synthesized for the application in perovskite solar cells (PSCs) and solid-state dye-sensitized solar cell (ssDSCs). The two HTMs were prepared through a facile two-step reaction from cheap starting material and with a total yield higher than 90%. These HTMs exhibit good solubility and charge-transport ability. PSCs based on HT2 achieved power conversion efficiency (PCE) of 18.04% under air conditions, which is comparable to that of the cell employing the commonly used Spiro-OMeTAD (18.27%), while HT1-based cell showed a slightly worse performance with a PCE of 17.18%. For ssDSCs, the HT2-based device yielded a PCE of 6.35%, which is also comparable to that of a cell fabricated based on Spiro-OMeTAD (6.36%). We found that the larger dimensional structure and molecular weight of HT2 enable better photovoltaic performance than that of the smaller one HT1. These results show that easily synthesized fluorene-based HTMs have great potential to replace the expensive Spiro-OMeTAD for both PSCs and ssDSCs.
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| 9. |
- Hultqvist, Adam, et al.
(författare)
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Atomic Layer Deposition of Electron Selective SnOx and ZnO Films on Mixed Halide Perovskite : Compatibility and Performance
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:35, s. 29707-29716
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Tidskriftsartikel (refereegranskat)abstract
- The compatibility of atomic layer deposition directly onto the mixed halide perovskite formamidinium lead iodide:methylammonium lead bromide (CH(NH2)(2), CH3NH3)Pb(I,Br)(3) (FAPbI(3):MAPbBr(3)) perovskite films is investigated by exposing the perovskite films to the full or partial atomic layer deposition processes for the electron selective layer candidates ZnO and SnOx. Exposing the samples to the heat, the vacuum, and even the counter reactant of H2O of the atomic layer deposition processes does not appear to alter the perovskite films in terms of crystallinity, but the choice of metal precursor is found to be critical. The Zn precursor Zn(C2H5)(2) either by itself or in combination with H2O during the ZnO atomic layer deposition (ALD) process is found to enhance the decomposition of the bulk of the perovskite film into PbI2 without even forming ZnO. In contrast, the Sn precursor Sn(N(CH3)(2))(4) does not seem to degrade the bulk of the perovskite film, and conformal SnOx films can successfully be grown on top of it using atomic layer deposition. Using this SnOx film as the electron selective layer in inverted perovskite solar cells results in a lower power conversion efficiency of 3.4% than the 8.4% for the reference devices using phenyl-C-70-butyric acid methyl ester. However, the devices with SnOx show strong hysteresis and can be pushed to an efficiency of 7.8% after biasing treatments. Still, these cells lacks both open circuit voltage and fill factor compared to the references, especially when thicker SnOx films are used. Upon further investigation, a possible cause of these losses could be that the perovskite/SnOx interface is not ideal and more specifically found to be rich in Sn, O, and halides, which is probably a result of the nucleation during the SnOx growth and which might introduce barriers or alter the band alignment for the transport of charge carriers.
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| 10. |
- Jeon, Il, et al.
(författare)
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Lithium-Ion Endohedral Fullerene (Li+@C-60) Dopants in Stable Perovskite Solar Cells Induce Instant Doping and Anti-Oxidation
- 2018
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 57:17, s. 4607-4611
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report use of [Li+@C-60]TFSI- as a dopant for spiro-MeOTAD in lead halide perovskite solar cells. This approach gave an air stability nearly 10-fold that of conventional devices using Li+TFSI-. Such high stability is attributed to the hydrophobic nature of [Li+@C-60]TFSI- repelling moisture and absorbing intruding oxygen, thereby protecting the perovskite device from degradation. Furthermore, [Li+@C-60]TFSI- could oxidize spiro-MeOTAD without the need for oxygen. The encapsulated devices exhibited outstanding air stability for more than 1000h while illuminated under ambient conditions.
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