| 1. |
- Calnan, Sonya, et al.
(författare)
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Development of Various Photovoltaic‐Driven Water Electrolysis Technologies for Green Solar Hydrogen Generation
- 2021
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- Direct solar hydrogen generation via a combination of photovoltaics (PV) and water electrolysis can potentially ensure a sustainable energy supply while minimizing greenhouse emissions. The PECSYS project aims at demonstrating asolar-driven electrochemical hydrogen generation system with an area >10 m2 with high efficiency and at reasonable cost. Thermally integrated PV electrolyzers(ECs) using thin-film silicon, undoped, and silver-doped Cu(In,Ga)Se2 and silicon heterojunction PV combined with alkaline electrolysis to form one unit are developed on a prototype level with solar collection areas in the range from 64 to2600 cm2 with the solar-to-hydrogen (StH) efficiency ranging from 4 to 13%. Electrical direct coupling of PV modules to a proton exchange membrane EC test the effects of bifacially (730 cm2 solar collection area) and to study the long-term operation under outdoor conditions (10 m2 collection area) is also investigated. In both cases, StH efficiencies exceeding 10% can be maintained over the test periods used. All the StH efficiencies reported are based on measured gas outflow using mass flow meters.
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| 2. |
- Cunha, Jose M. V., et al.
(författare)
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High-Performance and Industrially Viable Nanostructured SiOx Layers for Interface Passivation in Thin Film Solar Cells
- 2021
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Herein, it is demonstrated, by using industrial techniques, that a passivation layer with nanocontacts based on silicon oxide (SiOx) leads to significant improvements in the optoelectronical performance of ultrathin Cu(In,Ga)Se-2 (CIGS) solar cells. Two approaches are applied for contact patterning of the passivation layer: point contacts and line contacts. For two CIGS growth conditions, 550 and 500 degrees C, the SiOx passivation layer demonstrates positive passivation properties, which are supported by electrical simulations. Such positive effects lead to an increase in the light to power conversion efficiency value of 2.6% (absolute value) for passivated devices compared with a nonpassivated reference device. Strikingly, both passivation architectures present similar efficiency values. However, there is a trade-off between passivation effect and charge extraction, as demonstrated by the trade-off between open-circuit voltage (V-oc) and short-circuit current density (J(sc)) compared with fill factor (FF). For the first time, a fully industrial upscalable process combining SiOx as rear passivation layer deposited by chemical vapor deposition, with photolithography for line contacts, yields promising results toward high-performance and low-cost ultrathin CIGS solar cells with champion devices reaching efficiency values of 12%, demonstrating the potential of SiOx as a passivation material for energy conversion devices.
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| 3. |
- Ji, Jingjing, et al.
(författare)
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Developing Halogen-Free Polymer Donors for Efficient Nonfullerene Organic Solar Cells by Addition of Highly Electron-Deficient Diketopyrrolopyrrole Unit
- 2021
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Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 5:5
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Tidskriftsartikel (refereegranskat)abstract
- High-performance polymer donors when paired with nonfullerene acceptors are mainly limited to flanking halogenated benzodithiophene (BDT)-based π-conjugated copolymers, which however involve complex synthetic procedures. Herein, a series of halogen-free polymer donors that link BDT moiety with two highly electron-deficient benzodithiophene-dione (BDD) and diketopyrrolopyrrole (DPP) units with various molar ratios is developed. Compared with the benchmark PBDB-T donor containing BDD unit, additional incorporation of a stronger electron-negative DPP unit markedly lowers frontier molecular orbital levels and extends optical absorption, potentially leading to simultaneously enhanced VOC and JSC in organic solar cells. A remarkable power conversion efficiency (PCE) of 10.28% is thus obtained in the optimal P75 (BDD : DPP = 3:1 mol%) and Y6 blend cells in comparison with the reference PBDB-T:Y6 (9.20%). A slight addition of PC71BM into the blend is found to further generate finer phase-separated domains and thus increase the best efficiency up to 12.20%. The subtly critical roles of PC71BM are determined by transient absorption measurements on both thin-film and in situ devices to be the prolonged free charge carrier lifetime and the shallow charge transfer states, which enhance JSC and fill factor in the device, respectively.
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| 4. |
- Keller, Jan, et al.
(författare)
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Performance Limitations of Wide-Gap (Ag,Cu)(In,Ga)Se2 Thin-Film Solar Cells
- 2021
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 5:9
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Tidskriftsartikel (refereegranskat)abstract
- The effect of absorber stoichiometry in (Ag,Cu)(In,Ga)Se2(ACIGS) solar cells withbandgaps (Eg) > 1.40 eV is studied on a large sample set. It is conrmed thatmoving away in composition from ternary AgGaSe2by simultaneous reduction inGa and Ag content widens the chalcopyrite single-phase region and therebyreduces the amount of ordered vacancy compounds (OVCs). As a consequence, adistortion in currentvoltage characteristics, ascribed to OVCs at the back contact,can be successfully avoided. A clear anticorrelation between open-circuit voltage(VOC) and short-circuit current density (JSC) is detected with varying absorberstoichiometry, showing decreasingVOCand increasingJSCvalues for [I]/[III] > 0.9.Capacitance proling reveals that the absorber doping gradually decreases towardstoichiometric composition, eventually leading to complete depletion. It isobserved that only such fully depleted samples exhibit perfect carrier collection,evidencing a very low diffusion length in wide-gap ACIGS lms. The results indicatethat OVCs at the surface play a minor or passive role for device performance.Finally, a solar cell withVOC¼ 0.916 V atEg¼ 1.46 eV is measured, which is, to thebest of our knowledge, the highest value reported for this bandgap to date.
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| 5. |
- Shi, Yanan, et al.
(författare)
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Optimizing the Charge Carrier and Light Management of Nonfullerene Acceptors for Efficient Organic Solar Cells with Small Nonradiative Energy Losses
- 2021
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Ingår i: Solar RRL. - : WILEY-V C H VERLAG GMBH. - 2367-198X. ; 5:4
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Tidskriftsartikel (refereegranskat)abstract
- The photovoltaic properties and energy losses of organic solar cells (OSCs) based on nonfullerene acceptors (NFAs) are highly dependent on their molecular structures and aggregation morphologies. Charge carrier and light managements are important to optimize NFA molecules. Herein, four NFAs with different alkyl substituents and end groups, named BTP-C11-N2F, BTP-C9-N2F, BTP-C9-IC4F, and BTP-C9-N4F, are designed and synthesized by side-chain shortening, end-acceptor pi-extension, and fluorination. As a result, a favorable morphology is achieved in BTP-C9-N4F-based OSCs by using typical high bandgap polymer PM6 as a donor, and this system obtains the highest power conversion efficiency of 17.0% with a short circuit current (J(sc)) of 26.3 mA cm(-2), an open circuit current (V-oc) of 0.85 V, and a fill factor (FF) of 75.7%. In addition, its light (J(sc)) and charge carrier (V-oc x FF) managements relative to the Shockley-Queisser limit are also increased. Extending the conjugation of the end groups increased the energy levels of NFAs and enabled an E-loss of 0.50 eV with a nonradiative recombination loss of as low as 0.20 eV in BTP-C11-N2F-based OSCs. This work provides an efficient strategy to optimize the molecular structures of nonfullerene acceptors and further improve the properties of OSCs.
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| 6. |
- Song, Jiage, et al.
(författare)
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Over 13% Efficient Organic Solar Cells Based on Low-Cost Pentacyclic A-DA D-A-Type Nonfullerene Acceptor
- 2021
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Ingår i: Solar RRL. - : Wiley-Blackwell. - 2367-198X. ; 5:8
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies have almost focused on finding active layer materials with extended pi-conjugation structures for high-performance organic solar cells (OSCs). However, with the extension of conjugate length, the synthesis difficulty and cost of materials will increase. Achieving high efficiency while reducing material costs is a prerequisite for the commercialization of OSCs. Herein, two low-cost A-DA D-A-type (where A and D represent an electron-withdrawing unit and an electron-donating unit, respectively) nonfullerene acceptors (Y25,Y26) are synthesized with pentacyclic fused backbone as the DA D electron-deficient core and 5,6-difluoro-3-(dicyandiamethyl) indigo as the end groups. Compared with classical Y series acceptors with heptacyclic backbone, although Y25 and Y26 own the reduced conjugated length, they still show moderate performance (11.65% and 13.34%), and the cost of synthesis is significantly reduced. Therefore, we provide a new molecular design idea for commercially efficient nonfullerene OSCs acceptors. We also find that adding alkyl chains to the beta site of thiophenes is beneficial to obtaining the reduced energetic disorder, dominant molecular stacking, and desirable morphology, which can facilitate charge carrier transport and prompt higher short-circuit current density (J(sc)) as well as fill factor.
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| 7. |
- Zhang, Qilun, et al.
(författare)
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Understanding the Work Function Modification by a Self-assembled Polyvinylpyrrolidone Layer in Inverted Organic Solar Cells
- 2021
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Ingår i: Solar RRL. - : Wiley-VCH Verlagsgesellschaft. - 2367-198X. ; 5:1
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Tidskriftsartikel (refereegranskat)abstract
- Polyvinylpyrrolidone (PVP) has been successfully used as the cathode interfacial layer (CIL) in organic solar cells (OSCs) for work function (W-F) modification. However, detailed insight into the effect of a PVP interlayer on the physicochemical properties of the indium tin oxide (ITO) electrode in inverted OSCs (I-OSCs) is still largely absent. Herein, the ITO/PVP interface is investigated by photoelectron spectroscopy and the mechanisms for the energy level alignment of PVP on different substrates in general are unraveled. The results indicate that the dipole formation that reduces the W-F is driven by not only the directional intrinsic molecular dipole moments associated with the gamma-lactam of PVP, but also an additional dipole step with the same direction created by the image charges in the contacting (semi-)conductor layer. In addition, high-performance inverted OSCs (I-OSCs) are achieved by introducing a self-assembled ultrathin PVP layer using a simple immersion method. This work provides enhanced understanding of the PVP-based CIL and demonstrates its great potential in I-OSC fabrication, which can pave the way to simplified manufacturing of low-cost and large-area devices in organic electronic technologies.
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| 8. |
- Zhang, Xin, et al.
(författare)
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Enhancing the Photovoltaic Performance of Triplet Acceptors Enabled by Side-Chain Engineering
- 2021
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Ingår i: Solar RRL. - : WILEY-V C H VERLAG GMBH. - 2367-198X. ; 5:10
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Tidskriftsartikel (refereegranskat)abstract
- Triplet excitons have both longer lifetimes and diffusion lengths than singlet excitons due to the nature of triplet excitons, which is expected to increase the photocurrent and further improve the performance of organic solar cells (OSCs). However, the working mechanism of triplet excitons in OSCs is not clearly clarified. Therefore, it is urgent to develop new triplet acceptors for in-depth understanding. Herein, a series of acceptors (BTn-4Cl) are synthesized by fine-tuning of the side-chain branch positions. The generation of triplet excitons of BTn-4Cl is confirmed by the time-resolved photoluminescence (TRPL) spectra, magnetophotocurrent (MPC) experiment, and electron paramagnetic resonance (EPR) spectra. The effects of side-chain engineering on the optoelectronic properties, packing behaviors, energy losses, charge transport properties, spin lifetimes of triplet polarons, and blend film morphologies are systematically studied. These results show that D18:BT3-4Cl-based OSCs possess the best power conversion efficiency (PCE) of 17.31% due to lower energy losses, less recombination losses, more balanced charge carrier mobilities, longer spin-lattice (T-1) relaxation time, and more favorable morphology. This work enhances the understanding of the structure-property relationship for high-performance triplet acceptors.
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