| 1. |
- Gao, Jiajia, et al.
(författare)
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Light-induced electrolyte improvement in cobalt tris(bipyridine)-mediated dye-sensitized solar cells
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7:33, s. 19495-19505
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-ion-free tris(2,2′-bipyridine) Co(ii/iii)-mediated electrolytes have previously been proposed for long-term stable dye-sensitized solar cells (DSSCs). Such redox systems also offer an impressive DSSC performance improvement under light soaking exposure, manifested by an increase in photocurrent and fill factor without the expense of decreasing photovoltage. Kinetic studies show that charge transfer and ion diffusion at the electrode/electrolyte interface are improved due to the light exposure. Control experiments reveal that the light effect is unambiguously associated with electrolyte components, [Co(bpy)3]3+ and the Lewis-base additive tert-butylpyridine (TBP). Electrochemical and spectroscopic investigation of the [Co(bpy)3]3+/TBP mixtures points out that the presence of TBP, which retards the electrolyte diffusion, however causes an irreversible redox reaction of [Co(bpy)3]3+ upon light exposure that improves the overall conductivity. This discovery not only provides a new strategy to mitigate the typical Jsc-Voc trade-off in Co(ii/iii)-mediated DSSCs but also highlights the importance of investigating the photochemistry of a photoelectrochemical system.
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| 2. |
- Jain, Sagar Motilal, et al.
(författare)
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Vapor phase conversion of PbI2 to CH3NH3PbI3 : spectroscopic evidence for formation of an intermediate phase
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:7, s. 2630-2642
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Tidskriftsartikel (refereegranskat)abstract
- The formation of CH3NH3PbI3 (MAPbI(3)) from its precursors is probably the most significant step in the control of the quality of this semiconductor perovskite material, which is highly promising for photovoltaic applications. Here we investigated the transformation of spin coated PbI2 films to MAPbI(3) using a reaction with MAI in vapor phase, referred to as vapor assisted solution process (VASP). The presence of a mesoporous TiO2 scaffold on the substrate was found to speed up reaction and led to complete conversion of PbI2, while reaction on glass substrates was slower, with some PbI2 remaining even after prolonged reaction time. Based on data from UV-visible spectroscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, the formation of an X-ray amorphous intermediate phase is proposed, which is identified by an increasing absorption from 650 to 500 nm in the absorption spectrum. This feature disappears upon long reaction times for films on planar substrates, but persists for films on mesoporous TiO2. Poor solar cell performance of planar VASP prepared devices was ascribed to PbI2 remaining in the film, forming a barrier between the perovskite layer and the compact TiO2/FTO contact. Good performance, with efficiencies up to 13.3%, was obtained for VASP prepared devices on mesoporous TiO2.
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| 3. |
- Liu, Peng, et al.
(författare)
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The combination of a new organic D-pi-A dye with different organic hole-transport materials for efficient solid-state dye-sensitized solar cells
- 2015
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Ingår i: Journal of Materials Chemistry A. - : RSC Publishing. - 2050-7488 .- 2050-7496. ; 3:8, s. 4420-4427
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Tidskriftsartikel (refereegranskat)abstract
- A new organic donor-pi-acceptor sensitizer MKA253 has been applied for highly efficient solid-state dye-sensitized solar cells (ssDSSCs). Using 2,2',7,7'-tetrakis(N,N-di-pi-methoxyphenyl-amine) 9,9'-spirobifluorene (Spiro-OMeTAD) as the hole transport material (HTM), an excellent power conversion efficiency of 6.1% was recorded together with a high short-circuit current of 12.4 mA cm(-2) under standard AM 1.5G illumination (100 mW cm(-2)). Different combinations of dyes and HTMs have also been investigated in the ssDSSC device. The results showed that small molecule HTM based devices suffer from comparably high electron recombination losses, thus causing low open-circuit voltage. In addition, photo-induced absorption (PIA) spectroscopy showed that the small-molecule HTMs lead to more efficient dye regeneration in comparison with Spiro-OMeTAD, despite a lower thermodynamic driving force. The results of this study also show that optimized energy levels for the dye-HTMs could be a vital factor for highly efficient ssDSSCs.
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| 4. |
- Michaels, Hannes, et al.
(författare)
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Copper coordination polymers with selective hole conductivity
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 10:17, s. 9582-9591
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Tidskriftsartikel (refereegranskat)abstract
- Emerging technologies in solar energy will be critical in enabling worldwide society in overcoming the present energy challenges and reaching carbon net zero. Inefficient and unstable charge transport materials limit the current emerging energy conversion and storage technologies. Low-dimensional coordination polymers represent an alternative, unprecedented class of charge transport materials, comprised of molecular building blocks. Here, we provide a comprehensive study of mixed-valence coordination polymers from an analysis of the charge transport mechanism to their implementation as hole-conducting layers. Cu-II dithiocarbamate complexes afford morphology control of 1D polymer chains linked by (CuI2X2) copper halide rhombi. Concerted theoretical and experimental efforts identified the charge transport mechanism in the transition to band-like transport with a modeled effective hole mass of 6m(e). The iodide-bridged coordination polymer showed an excellent conductivity of 1 mS cm(-1) and a hole mobility of 5.8 10(-4) cm(2) (V s)(-1) at room temperature. Nanosecond selective hole injection into coordination polymer thin films was captured by nanosecond photoluminescence of halide perovskite films. Coordination polymers constitute a sustainable, tunable alternative to the current standard of heavily doped organic hole conductors.
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| 5. |
- Park, Byung-wook, et al.
(författare)
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Chemical engineering of methylammonium lead iodide/bromide perovskites : tuning of opto-electronic properties and photovoltaic performance
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:43, s. 21760-21771
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid (organic-inorganic) lead trihalide perovskites have attracted much attention in recent years due to their exceptionally promising potential for application in solar cells. Here a controlled one-step method is presented where PbCl2 is combined with three equivalents methylammonium halide (MAX, with X = land/or Br) in polar solvents to form MAPb(I-xBr(x))(3) perovskite films upon annealing in air at 145 degrees C. The procedure allows for a linear increment of the semiconductor bandgap from 1.60 eV to 2.33 eV by increasing the Br content. A transition from a tetragonal to a cubic structure is found when the Br fraction is larger than 0.3. X-ray photoelectron spectroscopy investigations shows that the increase of Br content is accompanied by a shift of the valence band edge to lower energy. Simultaneously, the conduction band moves to higher energy, but this shift is less pronounced. Time-resolved single-photon counting experiments of the perovskite materials on mesoporous TiO2 show faster decay kinetics for Br containing perovskites, indicative of improved electron injection into TiO2. Interestingly, kinetics of MAPb(12.7)Br(0.30)Cl(y) on TiO2 scaffold became faster after prolonged excitation during the measurement. In solar cell devices, MAPb(12.7)Br(0.30)), yielded best performance, giving more than 14% power conversion efficiency when used in combination with an n-type contact consisting of fluorine-doped tinoxide glass coated with dense TiO2 and a mesoporous Al2O3 scaffold, and a p-type contact, spiro-MeOTAD/Ag.
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| 6. |
- Sveinbjörnsson, Kári, et al.
(författare)
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Ambient air-processed mixed-ion perovskites for high-efficiency solar cells
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:42, s. 16536-16545
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Tidskriftsartikel (refereegranskat)abstract
- Mixed-ion (FAPbI(3))(1-x)(MAPbBr(3))(x) perovskite solar cells have achieved power conversion efficiencies surpassing 20%. However, in order to obtain these high efficiencies the preparation is performed in a controlled inert atmosphere. Here, we report a procedure for manufacturing highly efficient solar cells with a mixed-ion perovskite in ambient atmosphere. By including a heating step at moderate temperatures of the mesoporous titanium dioxide substrates, and spin-coating the perovskite solution on the warm substrates in ambient air, a red intermediate phase is obtained. Annealing the red phase at 100 degrees C results in a uniform and crystalline perovskite film, whose thickness is dependent on the substrate temperature prior to spin-coating. The temperature was optimized between 20 and 100 degrees C and it was observed that 50 degrees C substrate temperature yielded the best solar cell performances. The average efficiency of the best device was 17.6%, accounting for current-voltage (I-V) measurement hysteresis, with 18.8% performance in the backward scan direction and 16.4% in the forward scan direction. Our results show that it is possible to manufacture high-efficiency mixed-ion perovskite solar cells under ambient conditions, which is relevant for large-scale and low-cost device manufacturing processing.
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| 7. |
- Xu, Bo, et al.
(författare)
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Efficient solid state dye-sensitized solar cells based on an oligomer hole transport material and an organic dye
- 2013
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496 .- 0959-9428 .- 1364-5501. ; 1:46, s. 14467-14470
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Tidskriftsartikel (refereegranskat)abstract
- A low-cost and easily-synthesized organic hole transport material (HTM) X3 bearing triphenylamine units and an organic dye was utilized for solid state dye sensitized solar cells (ssDSCs), which have achieved the power conversion efficiencies of 5.8% and 7.1% under 1 sun and 0.46 sun, respectively, outperforming the ssDSC based on Spiro-OMeTAD 5.4% (1 sun) and 6.4% (0.46 sun).
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| 8. |
- Jiang, Roger, et al.
(författare)
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The Impact of Non-Uniform Photogeneration on Mass Transport in Dye-Sensitised Solar Cells
- 2018
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Ingår i: Journal of Materials Chemistry A. - 2050-7488. ; 6:22, s. 10264-10276
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Tidskriftsartikel (refereegranskat)abstract
- Following the introduction of cobalt(II/III)tris(2,2'-bipyridyl)-based redox mediators, dye-sensitised solar cells (DSSCs) have greatly advanced in power conversion efficiency (PCE). However, significant limiting factors include the fast electron recombination and slow mass transport of the oxidised redox mediator ([Co(bipy)(3)](3+)). In this work, the effect of non-uniform photogeneration on the mass transport of [Co(bipy)(3)](3+) through an electrolyte-infiltrated mesoporous TiO2 film was investigated. Different illumination conditions were used to control the photogeneration profile and the subsequent spatial distribution of [Co(bipy)(3)](3+) throughout the TiO2 film. They included parameters such as the light intensity, substrate-electrode/electrolyte-electrode (SE/EE) illumination direction, wavelength, and TiO2 photoanode thickness. Using large and small optical perturbation photocurrent transients, electron recombination kinetics with [Co(bipy)(3)](3+) were analysed in the time domain. Importantly, strong SE-absorption was shown to significantly contribute to the gradual depletion of [Co(bipy)(3)](3+) at the counter electrode, along with an increased film thickness and light intensity, resulting in excess recombination with [Co(bipy)(3)](3+) on the 10(-2)-1 s timescale. Furthermore, charge extraction current decay transients showed that a substantial amount of [Co(bipy)(3)](3+) can accumulate inside the TiO2 film, resulting in significant recombination at the collecting fluorine-doped tin oxide (FTO) contact on the 10(-3)-10(-2) s timescale. The sub-linear scaling of recombination with light intensity leads to deviating trends in charge extraction and electron transport measurements. Mass transport limitations and recombination losses at the FTO can be significantly reduced by maximising light absorption from the EE-side, which can increase PCE and reduce J-V hysteresis.
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