| 1. |
- Benesperi, Iacopo, et al.
(författare)
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Dynamic dimer copper coordination redox shuttles
- 2022
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Ingår i: Chem. - : Elsevier. - 2451-9308 .- 2451-9294. ; 8:2, s. 439-449
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Tidskriftsartikel (refereegranskat)abstract
- Summary Conventional redox mediators based on metal coordination complexes undergo electron transfer through the change in oxidation state of the metal center. However, electron transfer kinetics are offset toward preferred oxidation states when preorganized ligands constrain the reorganization of the coordination sphere. In contrast, we report here on dimeric copper(II/I) redox couples, wherein the extent of oxidation/reduction of two metal centers dictates the dynamic formation of dimer and monomer complexes: the dimeric (Cu(I))2 transitions to monomers of Cu(II). The bis(thiazole/pyrrole)-bipyridine tetradentate ligands stabilize both oxidation states of the unique redox systems. The dynamic dimer redox mediators offer a viable two-electron redox mechanism to develop efficient hybrid solar cells through inhibited recombination and rapid charge transport. Density functional theory calculations reveal inner reorganization energies for single-electron transfer as low as 0.27 eV, marking the dimeric complexes superior redox systems over single complexes as liquid and potentially solid-state electrolytes.
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| 2. |
- Benesperi, Iacopo, et al.
(författare)
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The researcher's guide to solid-state dye-sensitized solar cells
- 2018
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 6:44, s. 11903-11942
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Forskningsöversikt (refereegranskat)abstract
- In order to sustainably support its ever-increasing energy demand, the human society will have to harvest renewable energy wherever and whenever possible. When converting light to electricity, silicon solar cells are the technology of choice to harvest direct sunlight due to their high performance and continuously dropping price. For diffused light and indoor applications, however, silicon is not the material of choice. To power the next gizmo in your smart home, dye-sensitized solar cells (DSCs) are a viable alternative. Made from inexpensive, earth-abundant, and non-toxic materials, DSCs perform best at low light intensity. So far, issues such as leakage of the liquid electrolyte and its corrosive nature have limited the commercialization of this technology. To overcome these limitations, solid-state DSCs (ssDSCs) - in which the liquid electrolyte is replaced by a solid material - have been developed. For many years their efficiencies have been poor, preventing them from being widely employed. In the past six years, however, research efforts have led them to rival with their liquid counterparts. Here, we will review recent advancements in the field of ssDSCs. Every device component will be acknowledged, from metal oxides and new dyes to novel hole transporters, dopants, counter-electrodes and device architectures. After reviewing materials, long-term stability of devices will be addressed, finally giving an insight into the future that awaits this exciting technology.
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| 3. |
- Davison, Nathan, et al.
(författare)
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A room-temperature-stable electride and its reactivity : Reductive benzene/pyridine couplings and solvent-free Birch reductions
- 2023
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Ingår i: Chem. - : Elsevier. - 2451-9308 .- 2451-9294. ; 9:3, s. 576-591
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we report the synthesis of a room-temperature-stable electride (RoSE) reagent, namely K+(LiHMDS)e− (1) (HMDS: 1,1,1,3,3,3-hexamethyldisilazide), from accessible starting materials (potassium metal and LiHMDS) via mechanochemical ball milling at 20 mmol scale. Despite its amorphous nature, the presence of anionic electrons in 1, key diagnostic criteria for an electride, was confirmed by both experimental and computational studies. Therefore, by definition, 1 is an electride. Utilizing its anionic electrons, electride reagent 1 exhibited a versatile reactivity profile that includes (1) mediation of C–H activation and C–C coupling of benzene and pyridine and (2) mediation of solvent-free Birch reduction. This work proves the concept of facile mechanochemical synthesis of a room-temperature-stable electride, and it introduces electride 1 to the synthetic chemistry community as a versatile reagent.
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| 4. |
- Glinka, Adam, et al.
(författare)
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Interface Modification and Exceptionally Fast Regeneration in Copper Mediated Solar Cells Sensitized with Indoline Dyes
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 124:5, s. 2895-2906
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Tidskriftsartikel (refereegranskat)abstract
- The photovoltaic performance of solar cells sensitized with indoline D205 dye and its new derivative comprising an alkoxysilyl anchoring unit (D205Si) in the [Cu(tmby)(2)](TFSI)(2/1) (tmby = 4,4',6,6'-tetramethyl-2,2'-bipyridine, TFSI = bis(trifluoromethane)sulfonimide) redox couple mediated systems was studied in the presence of various titania/dye/electrolyte interface modifications. Cucurbit[7]uril (CB7) was employed to encapsulate dye molecules, creating an electronically insulating layer, suppressing electron interception by redox mediator, and leading to the increase in the electron lifetime in the titania conduction band. For example, the electron lifetime increased from 2.2 to 6.5 ms upon CB7 encapsulation of D205 cells at 0.9 V voltage. Further, molecular multicapping was optimized to minimize dye desorption and prevent electron recombination. As a result, photovoltaic performance was found to be enhanced by the interface modifications in most cases, especially when applied to the alkoxysilyl anchoring derivative. The charge transfer processes (dye regeneration, titania-dye and titania-redox mediator recombination) in the above-mentioned system and in the reference [Co(bpy)(3)](TFSI)(3/2) (bpy = 2,2'-bipyridine) redox couple mediated systems were investigated by means of small light perturbation electron lifetime measurements, electrochemical impedance spectroscopy, and nanosecond and femtosecond transient absorption spectroscopies. Indoline dyes were also found to be outstandingly fast regenerated by the Cu-based mediator (time constant shorter than 100 ns), which may open new opportunities for sensitizer improvements.
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| 5. |
- Jacobsson, Jesper, 1984-, et al.
(författare)
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An open-access database and analysis tool for perovskite solar cells based on the FAIR data principles
- 2022
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Ingår i: Nature Energy. - : Springer Nature. - 2058-7546. ; 7:1, s. 107-115
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Tidskriftsartikel (refereegranskat)abstract
- Large datasets are now ubiquitous as technology enables higher-throughput experiments, but rarely can a research field truly benefit from the research data generated due to inconsistent formatting, undocumented storage or improper dissemination. Here we extract all the meaningful device data from peer-reviewed papers on metal-halide perovskite solar cells published so far and make them available in a database. We collect data from over 42,400 photovoltaic devices with up to 100 parameters per device. We then develop open-source and accessible procedures to analyse the data, providing examples of insights that can be gleaned from the analysis of a large dataset. The database, graphics and analysis tools are made available to the community and will continue to evolve as an open-source initiative. This approach of extensively capturing the progress of an entire field, including sorting, interactive exploration and graphical representation of the data, will be applicable to many fields in materials science, engineering and biosciences.
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| 6. |
- Lindh, Linnea, et al.
(författare)
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Dye-sensitized solar cells based on Fe N-heterocyclic carbene photosensitizers with improved rod-like push-pull functionality
- 2021
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 12:48, s. 16035-16053
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Tidskriftsartikel (refereegranskat)abstract
- A new generation of octahedral iron(ii)-N-heterocyclic carbene (NHC) complexes, employing different tridentate C^N^C ligands, has been designed and synthesized as earth-abundant photosensitizers for dye sensitized solar cells (DSSCs) and related solar energy conversion applications. This work introduces a linearly aligned push-pull design principle that reaches from the ligand having nitrogen-based electron donors, over the Fe(ii) centre, to the ligand having an electron withdrawing carboxylic acid anchor group. A combination of spectroscopy, electrochemistry, and quantum chemical calculations demonstrate the improved molecular excited state properties in terms of a broader absorption spectrum compared to the reference complex, as well as directional charge-transfer displacement of the lowest excited state towards the semiconductor substrate in accordance with the push-pull design. Prototype DSSCs based on one of the new Fe NHC photosensitizers demonstrate a power conversion efficiency exceeding 1% already for a basic DSSC set-up using only the I−/I3−redox mediator and standard operating conditions, outcompeting the corresponding DSSC based on the homoleptic reference complex. Transient photovoltage measurements confirmed that adding the co-sensitizer chenodeoxycholic acid helped in improving the efficiency by increasing the electron lifetime in TiO2. Time-resolved spectroscopy revealed spectral signatures for successful ultrafast (<100 fs) interfacial electron injection from the heteroleptic dyes to TiO2. However, an ultrafast recombination process results in undesirable fast charge recombination from TiO2back to the oxidized dye, leaving only 5-10% of the initially excited dyes available to contribute to a current in the DSSC. On slower timescales, time-resolved spectroscopy also found that the recombination dynamics (longer than 40 μs) were significantly slower than the regeneration of the oxidized dye by the redox mediator (6-8 μs). Therefore it is the ultrafast recombination down to fs-timescales, between the oxidized dye and the injected electron, that remains as one of the main bottlenecks to be targeted for achieving further improved solar energy conversion efficiencies in future work.
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| 7. |
- Michaels, Hannes, 1994-
(författare)
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A molecular guide to efficient charge transport : Coordination materials for photovoltaic cells
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Emerging solar energy conversion and energy storage technologies play a vital role in solving the present energy crisis and achieving carbon net zero. Currently, they are limited by the use of inefficient, unstable and expensive charge transport materials. The development of new charge transport materials is still far behind the efforts that have been made to develop the light-absorbing or other components. Metalorganic coordination compounds offer unique sets of properties as hybrids between conductive metals and tunable organic molecules. The coordination of the metal centers is crucial to control in order to maximise the solar cell efficiency - or undesired electronic recombination limits the power output. Tetradentate ligands allow copper complexes to dynamically switch between dimers or monomers, pending the oxidation state of the metal ions. The high energy barrier for the reduction of CuII monomers prevents electron transfer across the TiO2|dye|electrolyte interface: Interfacial recombination is reduced and the dye-sensitised solar cells achieve greater photovoltages. Coordination complexes linked into low-dimensional coordination polymers afford charge transport with an electrical conductivity as high as 0.1 S m-1 via band-like conduction at room temperature, needless of cationic dopants. The polymers rapidly extract photoexcited charges from halide perovskite films. 14% power conversion efficiency were recorded from a perovskite solar cell based on a carbon counter electrode. The solar cell stability was much increased compared to heavily doped organic hole conductors. Emerging dye-sensitised solar cells excel especially under ambient conditions, and have been proposed as power sources for dispatched electronic devices (the Internet of things), in place of single-use and difficult-to-recycle batteries. Through tailoring of the optical response and the electrolyte composition, power conversion efficiencies of 37.5% with photovoltages of 1.00 V at 1000 lux (fluorescent lamp) are demonstrated. The increased performance is identified to stem from reduced interfacial recombination by transient photovoltage methods as well as electrochemical impedance spectroscopy. A series of prototype tests underline the feasibility of light harvesters as power sources for electronic devices, executing sophisticated computation tasks such as machine learning. The devices self-optimise their energy consumption; adaptive sleep and small supercapacitors allow to sustain device operation during periods of fluctuating energy availability.
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| 8. |
- Michaels, Hannes, et al.
(författare)
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Assessment of TiO2 Blocking Layers for CuII/I-Electrolyte Dye-Sensitized Solar Cells by Electrochemical Impedance Spectroscopy
- 2022
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 5:2, s. 1933-1941
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Tidskriftsartikel (refereegranskat)abstract
- The TiO2 blocking layer in dye-sensitized solar cells is the most difficult component to evaluate at thicknesses below 50 nm, but it is crucial for the power conversion efficiency. Here, the electrode capacitance of TiO2 blocking layers is tested in aqueous [Fe(CN)6]3–/4– and correlated to the performance of photoanodes in devices based on a [Cu(tmby)2]2+/+ electrolyte. The effects of the blocking layer on electronic recombination in the devices are illustrated with transient photovoltage methods and electrochemical impedance analysis. We have thus demonstrated a feasible and facile method to assess TiO2 blocking layers for the fabrication of dye-sensitized solar cells.
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| 9. |
- Michaels, Hannes, et al.
(författare)
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Challenges and prospects of ambient hybrid solar cell applications
- 2021
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6520 .- 2041-6539. ; 12:14, s. 5002-5015
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Forskningsöversikt (refereegranskat)abstract
- The impending implementation of billions of Internet of Things and wireless sensor network devices has the potential to be the next digital revolution, if energy consumption and sustainability constraints can be overcome. Ambient photovoltaics provide vast universal energy that can be used to realise near-perpetual intelligent IoT devices which can directly transform diffused light energy into computational inferences based on artificial neural networks and machine learning. At the same time, a new architecture and energy model needs to be developed for IoT devices to optimize their ability to sense, interact, and anticipate. We address the state-of-the-art materials for indoor photovoltaics, with a particular focus on dye-sensitized solar cells, and their effect on the architecture of next generation IoT devices and sensor networks.
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| 10. |
- Michaels, Hannes, et al.
(författare)
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Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells
- 2018
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Ingår i: Inorganics. - : MDPI AG. - 2304-6740. ; 6:2
-
Tidskriftsartikel (refereegranskat)abstract
- In dye-sensitized solar cells (DSCs), the redox mediator is responsible for the regeneration of the oxidized dye and for the hole transport towards the cathode. Here, we introduce new copper complexes with tetradentate 6,6-bis(4-(S)-isopropyl-2-oxazolinyl)-2,2-bipyridine ligands, Cu(oxabpy), as redox mediators. Copper coordination complexes with a square-planar geometry show low reorganization energies and thus introduce smaller losses in photovoltage. Slow recombination kinetics of excited electrons between the TiO2 and Cu-II(oxabpy) species lead to an exceptionally long electron lifetime, a high Fermi level in the TiO2, and a high photovoltage of 920 mV with photocurrents of 10 mA.cm(-2) and 6.2% power conversion efficiency. Meanwhile, a large driving force remains for the dye regeneration of the Y123 dye with high efficiencies. The square-planar Cu(oxabpy) complexes yield viscous gel-like solutions. The unique charge transport characteristics are attributed to a superposition of diffusion and electronic conduction. An enhancement in charge transport performance of 70% despite the higher viscosity is observed upon comparison of Cu(oxabpy) to the previously reported Cu(tmby)(2) redox electrolyte.
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| 11. |
- 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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| 12. |
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| 13. |
- Michaels, Hannes, et al.
(författare)
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Dye-sensitized solar cells under ambient light powering machine learning : towards autonomous smart sensors for the internet of things
- 2020
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Ingår i: Chemical Science. - : ROYAL SOC CHEMISTRY. - 2041-6520 .- 2041-6539. ; 11:11, s. 2895-2906
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Tidskriftsartikel (refereegranskat)abstract
- The field of photovoltaics gives the opportunity to make our buildings "smart'' and our portable devices "independent", provided effective energy sources can be developed for use in ambient indoor conditions. To address this important issue, ambient light photovoltaic cells were developed to power autonomous Internet of Things (IoT) devices, capable of machine learning, allowing the on-device implementation of artificial intelligence. Through a novel co-sensitization strategy, we tailored dye-sensitized photovoltaic cells based on a copper(II/I) electrolyte for the generation of power under ambient lighting with an unprecedented conversion efficiency (34%, 103 mu W cm(-2) at 1000 lux; 32.7%, 50 mu W cm(-2) at 500 lux and 31.4%, 19 mu W cm(-2) at 200 lux from a fluorescent lamp). A small array of DSCs with a joint active area of 16 cm(2) was then used to power machine learning on wireless nodes. The collection of 0.947 mJ or 2.72 x 10(15) photons is needed to compute one inference of a pre-trained artificial neural network for MNIST image classification in the employed set up. The inference accuracy of the network exceeded 90% for standard test images and 80% using camera-acquired printed MNIST-digits. Quantization of the neural network significantly reduced memory requirements with a less than 0.1% loss in accuracy compared to a full-precision network, making machine learning inferences on low-power microcontrollers possible. 152 J or 4.41 x 10(20) photons required for training and verification of an artificial neural network were harvested with 64 cm(2) photovoltaic area in less than 24 hours under 1000 lux illumination. Ambient light harvesters provide a new generation of self-powered and "smart" IoT devices powered through an energy source that is largely untapped.
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| 14. |
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| 15. |
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| 16. |
- Mogensen, Josefine, et al.
(författare)
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Indenofluorene-Extended Tetrathiafulvalene Scaffolds for Dye-Sensitized Solar Cells
- 2020
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 2020:38, s. 6127-6134
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Tidskriftsartikel (refereegranskat)abstract
- Indenofluorene‐extended tetrathiafulvalenes (IF‐TTFs) comprise a class of π‐conjugated sensitizers that exhibit strong absorptions in the visible region and two reversible one‐electron oxidations. Herein we present the synthesis and optical as well as redox properties of novel IF‐TTF donor‐acceptor scaffolds that were integrated in dye‐sensitized solar cells (DSCs) via anchoring of a carboxylic acid end‐group on the scaffolds to TiO2. Synthetically, the scaffolds were constructed by Sonogashira coupling reactions between an iodo‐functionalized IF‐TTF and an acceptor moeity containing a terminal alkyne. These very first IF‐TTF based candidates for DSCs exhibited high performances, in particular a dye incorporating a benzothiadiazole acceptor moiety, showing a conversion efficiency of 6.4 %. This result signals that IF‐TTF derivatives present a promising class of compounds for further structural modifications. Such modifications will benefit from the readiness of the iodo‐funcitonalized IF‐TTF building block to undergo Pd‐catalyzed coupling reactions.
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| 17. |
- Morritt, G. H., et al.
(författare)
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Coordination polymers for emerging molecular devices
- 2022
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Ingår i: Chemical Physics Reviews. - : American Institute of Physics (AIP). - 2688-4070. ; 3:1
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Forskningsöversikt (refereegranskat)abstract
- Conductive coordination polymers are hybrid materials with the potential to be implemented in the next generation of electronic devices, owing to several desirable properties. A decade ago, only a few scattered examples exhibiting conductivity existed within this class of materials, yet today groups of coordination polymers possess electrical conductivities and mobilities that rival those of inorganic semiconductors. Many currently emerging energy harvesting and storage technologies are limited by the use of inefficient, unstable, and unsustainable charge transport materials with little tunability. Coordination polymers, on the other hand, offer great electrical properties and fine-tunability through their assembly from molecular building blocks. Herein, the structure-function relationship of these building blocks and how to characterize the resulting materials are examined. Solution processability allows devices to step away drastically from conventional fabrication methods and enables cheap production from earth abundant materials. The ability to tune the electrical and structural properties through modifications at the molecular level during the material synthesis stages allows for a large design space, opening the door to a wide spectrum of applications in environmentally friendly technologies, such as molecular wires, photovoltaics, batteries, and sensors. Sustainable, high-performing charge transport materials are crucial for the continued advance of emerging molecular technologies. This review aims to provide examples of how the promising properties of coordination polymers have been exploited to accelerate the development of molecular devices.
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| 18. |
- Saygili, Yasemin, et al.
(författare)
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Effect of Coordination Sphere Geometry of Copper Redox Mediators on Regeneration and Recombination Behavior in Dye-Sensitized Solar Cell Applications
- 2018
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:9, s. 4950-4962
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Tidskriftsartikel (refereegranskat)abstract
- The recombination of injected electrons with oxidized redox species and regeneration behavior of copper redox mediators are investigated for four copper complexes, [Cu(dmby)(2)](2+/1+) (dmby = 6,6'-dimethyl-2,2'-bipyridine), [Cu(tmby)(2)](2+/1+) (tmby = 4,4',6,6'- tetramethyl-2,2'-bipyridine), [Cu(eto)(2)](2+/1+) (eto = 4-ethoxy-6,6'-dimethyl-2,2'-bipyridine), and [Cu(dmp)(2)](2+/1+) (dmp = bis(2,9-dimethyl-1,10-phenantroline). These complexes were examined in conjunction with the D5, D35, and D45 sensitizers, having various degrees of blocking moieties. The experimental results were further supported by density functional theory calculations, showing that the low reorganization energies, lambda, of tetra-coordinated Cu(I) species (lambda = 0.31-0.34 eV) allow efficient regeneration of the oxidized dye at driving forces down to approximately 0.1 eV. The regeneration electron transfer reaction is in the Marcus normal regime. However, for Cu(II) species, the presence of 4-tertbutylpyridine (TBP) in electrolyte medium results in penta-coordinated complexes with altered charge recombination kinetics (lambda = 1.23-1.40 eV). These higher reorganization energies lead to charge recombination in the Marcus normal regime instead of the Marcus inverted regime that could have been expected from the large driving force for electrons in the conduction band of TiO2 to react with Cu(II). Nevertheless, the recombination resistance and electron lifetime values were higher for the copper redox species compared to the reference cobalt redox mediator. The DSC devices employing D35 dye with [Cu(dmp)(2)](2+/1+) reached a record value for the open circuit voltage of 1.14 V without compromising the short circuit current density value. Even with the D5 dye, which lacks recombination preventing steric units, we reached 7.5% efficiency by employing [Cu(dmp)(2)](2+/1+) and [Cu(dmby)(2)](2+/1+) at AM 1.5G full sun illumination with open circuit voltage values as high as 1.13 V.
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| 19. |
- Sutton, Matthew, et al.
(författare)
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Rapid and Facile Fabrication of Polyiodide Solid-State Dye-Sensitized Solar Cells Using Ambient Air Drying
- 2022
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 14:38, s. 43456-43462
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized solar cells are promising candidates for low-cost indoor power generation applications. However, they currently suffer from complex fabrication and stability issues arising from the liquid electrolyte. Consequently, the so-called zombie cell was developed, in which the liquid electrolyte is dried out to yield a solid through a pinhole after cell assembly. We report a method for faster, simpler, and potentially more reliable production of zombie cells through direct and rapid drying of the electrolyte on the working electrode prior to cell assembly, using an iodide-triiodide redox couple electrolyte as a basis. These "rapid-zombie" cells were fabricated with power conversion efficiencies reaching 5.0%, which was larger than the 4.5% achieved for equivalent "slow" zombie cells. On a large-area cell of 15.68 cm(2), over 2% efficiency was achieved at 0.2 suns. After 12 months of dark storage, the "rapid-zombie" cells were remarkably stable and actually showed a moderate increase in average efficiencies.
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| 20. |
- Tanaka, Ellie, et al.
(författare)
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Synergy of co-sensitizers in a copper bipyridyl redox system for efficient and cost-effective dye-sensitized solar cells in solar and ambient light
- 2020
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Ingår i: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 8:3, s. 1279-1287
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Tidskriftsartikel (refereegranskat)abstract
- Dye-sensitized solar cells (DSSCs) have a great potential to expand the area of photovoltaics towards portable or indoor applications. Since the dye is one of the most costly components in the device, it is always of interest to find ways to lower its associated cost. Here, we propose the co-sensitization technique as a simple and effective solution towards this aim. A less-expensive pi-A dye (5T) was mixed with a better-performing D-A-pi-A dye (XY1) to fabricate the co-sensitized devices (XY1 + 5T). The dyes were combined with a Cu-I/II(tmby)(2) (tmby = (4,4 ',6,6 '-tetramethyl-2,2 '-bipyridine)) electrolyte and tested at 1 sun and 0.1 sun conditions. The XY1 + 5T devices showed similar power conversion efficiency (PCE) to that of the XY1-only devices at 1 sun (avg. 9.1%), and superior PCE at 0.1 sun (avg. 9.4% vs. 8.6%). The charge transport behaviour in the devices was investigated through a combination of photophysical measurements, which revealed complementary effects of both dyes during device operation. The performance of XY1 + 5T at lower light intensity was further assessed using artificial fluorescent lighting, which marked a PCE as high as 29.2% at 1000 lux, among the highest reported. Finally, the cost of dye was estimated to be reduced by ca. 30% if an XY1-only device is replaced by XY1 + 5T with no loss in efficiency. The cost-performance is thus improved 1.4 times. Our findings will revalue the co-sensitization method as a means to address the challenges of DSSC commercialization.
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| 21. |
- Thyr, Jakob, 1979-, et al.
(författare)
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Quantum Capacitance and Electrochemical Density of States in Quantum Confined ZnO
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Quantum confined semiconductors have been of interest the last decades, largely fueled bythe unique ability to tune the electronic properties, and thereby their optical response. Anotherconsequence of their low dimensions is the markedly increased surface area that canbe utilized in surface dependent phenomena such as in sensors or catalysis. In this study,zinc oxide quantum dots (Qdots) were synthesized in the size regime from 3.9 nm to 6.4 nm,with a resulting optical bandgap change from 3.61 eV to 3.43 eV. Their vibrational quantumconfinement and surface modes were assessed with Raman spectroscopy, and differentialpulse voltammetry was utilized to extract the electrochemical bandgap, the CB edge position,and the electrochemical density of states (DOS). The quantum capacitive dependence on theelectrochemical DOS is analyzed together with the potentiostatically induced Burstein-Mossshift to extract details in the conduction band (CB) properties of the Qdots. The successivenarrowing and change of density of states at the CB reveal a size dependent quantum capacitance,originating in the decrease of the electrochemically accessible states for the ZnO Qdotsupon their decrease in size.
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| 22. |
- Yuan, Lin, et al.
(författare)
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Four-Terminal Tandem Solar Cell with Dye-Sensitized and PbS Colloidal Quantum-Dot-Based Subcells
- 2020
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Ingår i: ACS Applied Energy Materials. - : AMER CHEMICAL SOC. - 2574-0962. ; 3:4, s. 3157-3161
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Tidskriftsartikel (refereegranskat)abstract
- In this work, high-performance four-terminal solution-processed tandem solar cells were fabricated by using dye-sensitized solar cells (DSSCs) as top-cells and lead sulfide (PbS) colloidal quantum dot solar cells (CQDSCs) as bottom-cells. For dye-sensitized top-cells, three different dye combinations were used while the titanium dioxide (TiO2) scattering layer was removed to maximize the transmission. For the PbS bottom-cells, quantum dots with different sizes were compared. Over 12% power conversion efficiency has been achieved by using the XL dye mixture and 890 nm PbS QDs, which shows a significant efficiency enhancement when compared to single DSSC or CQDSC subcells.
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