| 311. |
- Rodriguez Martinez, Xabier, et al.
(författare)
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Air Processing of Thick and Semitransparent Laminated Polymer:Non-Fullerene Acceptor Blends Introduces Asymmetric Current-Voltage Characteristics
- 2023
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 33:27
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Tidskriftsartikel (refereegranskat)abstract
- Non-fullerene acceptors have recently revolutionized indoor organic photovoltaics (OPVs) with power conversion efficiencies exceeding 30% in laboratory scale. Nevertheless, transferring their superior performance to larger-scale prototyping, i.e., air-processing via roll-to-roll compatible techniques, still shows severe challenges. Herein, the industrial potential of the PM6:IO4Cl blend, which is one of the most successful indoor OPV photoactive layers (PALs), is thoroughly investigated. The corresponding thick and semitransparent laminated devices are fabricated entirely in air, by blade and slot-die coating. Their current-voltage (J-V) characteristics show anomalous features depending on the illumination side, with the cathode side generally outperforming the anode counterpart. Electrical and optical modeling reveal that a plausible cause of such a phenomenon is a dead layer that forms at the PAL/anode contact interface that does not contribute to the photocurrent. Said layer becomes undetectable when the PALs are made thin enough (<35 nm each) leading to symmetric J-V curves and improved light utilization efficiency. By screening the photovoltaic performance of multiple donor:acceptor blends, certain all-polymer and polymer:fullerene PALs are identified as adequately symmetric candidates for thick device up-scaling. Finally, ternary blends based on PM6:IO4Cl:fullerene may constitute a viable route to mitigate the electrical asymmetry detected on conventional binary blends.
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| 312. |
- Rodriguez Martinez, Xabier, et al.
(författare)
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Laminated Organic Photovoltaic Modules for Agrivoltaics and Beyond: An Outdoor Stability Study of All-Polymer and Polymer:Small Molecule Blends
- 2023
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Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 33:10
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Tidskriftsartikel (refereegranskat)abstract
- The integration of organic photovoltaic (OPV) modules on greenhouses is an encouraging practice to offset the energy demands of crop growth and provide extra functionality to dedicated farmland. Nevertheless, such OPV devices must meet certain optical and stability requirements to turn net zero energy greenhouse systems a reality. Here a donor:acceptor polymer blend is optimized for its use in laminated devices while matching the optical needs of crops. Optical modeling is performed and a greenhouse figure-of-merit is introduced to benchmark the trade-off between photovoltaic performance and transparency for both chloroplasts and humans. Balanced donor:acceptor ratios result in better-performing and more thermally stable devices than acceptor-enriched counterparts. The optimized polymer blend and state-of-the-art polymer:small-molecule blends are next transferred to 25 cm(2) laminated modules processed entirely from solution and in ambient conditions. The modules are mounted on a greenhouse as standalone or 4-terminal tandem configurations and their outdoor stability is tracked for months. The study reveals degradation modes undetectable under laboratory conditions such as module delamination, which accounts for 10-20% loss in active area. Among the active layers tested, polymer:fullerene blends are the most stable and position as robust light harvesters in future building-integrated OPV systems.
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| 313. |
- Rodriguez Martinez, Xabier, et al.
(författare)
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Matching electron transport layers with a non-halogenated and low synthetic complexity polymer:fullerene blend for efficient outdoor and indoor organic photovoltaics
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 10:19, s. 10768-10779
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Tidskriftsartikel (refereegranskat)abstract
- The desired attributes of organic photovoltaics (OPV) as a low cost and sustainable energy harvesting technology demand the use of non-halogenated solvent processing for the photoactive layer (PAL) materials, preferably of low synthetic complexity (SC) and without compromising the power conversion efficiency (PCE). Despite their record PCEs, most donor-acceptor conjugated copolymers in combination with non-fullerene acceptors are still far from upscaling due to their high cost and SC. Here we present a non-halogenated and low SC ink formulation for the PAL of organic solar cells, comprising PTQ10 and PC61BM as donor and acceptor materials, respectively, showing a record PCE of 7.5% in blade coated devices under 1 sun, and 19.9% under indoor LED conditions. We further study the compatibility of the PAL with 5 different electron transport layers (ETLs) in inverted architecture. We identify that commercial ZnO-based formulations together with a methanol-based polyethyleneimine-Zn (PEI-Zn) chelated ETL ink are the most suitable interlayers for outdoor conditions, providing fill factors as high as 74% and excellent thickness tolerance (up to 150 nm for the ETL, and >200 nm for the PAL). In indoor environments, SnO2 shows superior performance as it does not require UV photoactivation. Semi-transparent devices manufactured entirely in air via lamination show indoor PCEs exceeding 10% while retaining more than 80% of the initial performance after 400 and 350 hours of thermal and light stress, respectively. As a result, PTQ10:PC61BM combined with either PEI-Zn or SnO2 is currently positioned as a promising system for industrialisation of low cost, multipurpose OPV modules.
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| 314. |
- Rodriguez-Martinez, Xabier, et al.
(författare)
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Microfluidic-Assisted Blade Coating of Compositional Libraries for Combinatorial Applications: The Case of Organic Photovoltaics
- 2020
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 10:33
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Tidskriftsartikel (refereegranskat)abstract
- Microfluidic technologies are highly adept at generating controllable compositional gradients in fluids, a feature that has accelerated the understanding of the importance of chemical gradients in biological processes. That said, the development of versatile methods to generate controllable compositional gradients in the solid-state has been far more elusive. The ability to produce such gradients would provide access to extensive compositional libraries, thus enabling the high-throughput exploration of the parametric landscape of functional solids and devices in a resource-, time-, and cost-efficient manner. Herein, the synergic integration of microfluidic technologies is reported with blade coating to enable the controlled formation of compositional lateral gradients in solution. Subsequently, the transformation of liquid-based compositional gradients into solid-state thin films using this method is demonstrated. To demonstrate efficacy of the approach, microfluidic-assisted blade coating is used to optimize blending ratios in organic solar cells. Importantly, this novel technology can be easily extended to other solution processable systems that require the formation of solid-state compositional lateral gradients.
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| 315. |
- Roman, LS, et al.
(författare)
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Photovoltaic devices based on photo induced charge transfer in polythiophene : CN-PPV blends
- 2003
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Ingår i: Brazilian journal of physics. - 0103-9733 .- 1678-4448. ; 33:2, s. 376-381
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the photovoltaic properties of polymer devices based on a blend of two polymers, (poly(3-(2'-methoxy-5'-octylphenyl) thiophene) (POMeOPT) and poly(2,5,2',5'-tetrahexyloxy-7,8'-dicyanodi-p-phenylenevinylene) (CN-PPV), where photo induced charge transfer takes place at the interfaces formed by the interpenetrating network of the donor and the acceptor. The polymer blend films resulting from the spin coating were phase separated and the photo response of the devices depended on the morphology of the segregation. We have studied different blend ratios by photoluminescence quenching, scanning force microscopy and photovoltaic measurements. External quantum efficiencies of 4.5% at 500nm were achieved for the less segregated polymer blend.
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| 316. |
- Roman, L.S., et al.
(författare)
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Charge carrier mobility in substituted polythiophene-based diodes
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 125:3, s. 419-422
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the transport properties of the semiconducting polymer poly(3-(2'-methoxy-5'-octylphenyl)thiophene) (POMeOPT). We have measured the current-voltage (C-V) characteristics of single polymer layer devices in two regimes contact limited current and bulk-limited current. The passage from one regime to the other was done upon insertion of a conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT-PSS) between the metallic electrode and the semiconducting polymer. With PEDOT-PSS as electrode, the polymer gave space-charge limited current (SCLC) with the mobility dependent on electric field. Fitting the data, we were able to obtain important parameters, such as the zero-field mobility and the characteristic field. We have compared our results with the well-studied polymer poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) in similar experiments earlier reported. © 2001 Elsevier Science B.V. All rights reserved.
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| 317. |
- Roman, L.S., et al.
(författare)
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Polymer diodes with high rectification
- 1999
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Ingår i: Applied Physics Letters. - 0003-6951 .- 1077-3118. ; 75, s. 3557-3557
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Tidskriftsartikel (refereegranskat)
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| 318. |
- Roman, LS, et al.
(författare)
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Trapping light in polymer photodiodes with soft embossed gratings
- 2000
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 12:3, s. 189-
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Tidskriftsartikel (refereegranskat)abstract
- Increasing the conversion efficiency is very important in photovoltaic devices, as is cheap and simple technology. Here is demonstrated a soft embossing technique for printing a submicrometer grating with an elastomeric mold into an optically active polymer layer in a photovoltaic device (see Figure). The light trapping due to the grating pattern enhances the photoconversion efficiency by more than 25 % at normal light incidence (see also inside front cover).
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| 319. |
- Ruseckas, A, et al.
(författare)
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Intra- and interchain luminescence in amorphous and semicrystalline films of phenyl-substituted polythiophene
- 2001
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Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 105:32, s. 7624-7631
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Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence (PL) measurements of spin-cast amorphous films of a regioregular polythiophene derivative poly[3-(4-octylphenyl)thiophene] and of annealed semicrystalline films of the same polymer with an interchain stacking distance of 5 Angstrom. Red-shifted PL appears at long delay times in both pristine and annealed films, which we assign to interchain aggregates populated by excitation energy migration. Aggregate luminescence in annealed films exhibits a pronounced vibronic structure indicating the coupling to a C=C bond stretch with a Huang-Rhys factor S = 2. Two types of aggregates are distinguished in annealed films: in a few picoseconds most excitations are trapped by aggregates with a large energy gap (about 1.83 eV) between the lowest excited singlet state and the ground state. Excitation energy is transferred or the aggregates relax structurally with a time constant of about 200 ps to aggregates with a smaller energy gap (about 1.75 eV). The radiative lifetime of aggregates with smaller energy gap is estimated to be about 35 ns, two times longer than that of aggregates with the larger energy gap. In spin-cast amorphous films, emission from intrachain singlet excitons has a longer lifetime than in annealed films and only high-energy-gap aggregates are populated.
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| 320. |
- Ruseckas, A., et al.
(författare)
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Luminescence from inter-chain aggregates in polythiophene films
- 2001
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Ingår i: Synthetic Metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 603-604
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Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence of two polythiophene derivatives with different chain packing. Emission of inter-chain aggregates is distinguished from that of intra-chain singlet excitons. The aggregate luminescence is shifted towards lower energies relative to that of intra-chain exciton by 0.17 eV, and the Huang-Rhys factor of the coupling to the intra-chain C double bondC vibration is S = 1.5. The excitonic coupling in aggregates is of intermediate strength.
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