| 1. |
- Alkadir Abdulahi, Birhan, 1985, et al.
(författare)
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Open-Circuit Voltage Modulations on All-Polymer Solar Cells by Side Chain Engineering on 4,8-Di(thiophen-2-yl)benzo[1,2- b:4,5- b′]dithiophene-Based Donor Polymers
- 2018
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:6, s. 2918-2926
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, all-polymer solar cells (all-PSCs), incorporating active layers based on blends of electron-donor (D) and acceptor (A) polymers, have drawn attention because of the advantages they hold in the flexibility of choosing the D:A combinations to modulate their energy levels and to improve their overall open-circuit voltages (V oc ) and power conversion efficiencies (PCE)s. V oc is one of the key parameters for the determination of the PCEs of PSCs. In this work, we synthesized six donor polymers with three different side chains appended to the 4,8-di(thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDT) units. By substituting carbon with sulfur and silicon atoms at the 5-position of the thiophenes attached to the BDT units, the highest occupied molecular orbital (HOMO) levels of the donor polymers could be successfully lowered. As anticipated, the V oc values of the resulting all-PSCs increased along with the lowering of the HOMO levels of the donor polymers. Among the six all-PSCs, the PBDT-BDD:PNDI-T10 all-PSC realized a balance between the photovoltage and photocurrent, where a decent PCE of 5.6% was obtained with a V oc of 0.9 V and a photocurrent of 10.5 mA/cm 2 .
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| 2. |
- Alkadir Abdulahi, Birhan, 1985, et al.
(författare)
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Structural engineering of pyrrolo[3,4-: F] benzotriazole-5,7(2 H,6 H)-dione-based polymers for non-fullerene organic solar cells with an efficiency over 12%
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 7:33, s. 19522-19530
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have synthesized two wide band gap donor polymers based on benzo[1,2-b:4,5-b′]dithiophene (BDT) and pyrrolo[3,4-f]benzotriazole-5,7(2H,6H)-dione (TzBI), namely, PBDT-TzBI and PBDT-F-TzBI and studied their photovoltaic properties by blending them with ITIC as an acceptor. Polymer solar cell devices made from PBDT-TzBI:ITIC and PBDT-F-TzBI:ITIC exhibited power conversion efficiencies (PCEs) of 9.22% and 11.02% and while annealing at 160 °C, improved the device performances to 10.24% and 11.98%, respectively. Upon solvent annealing with diphenyl ether (DPE) (0.5%) and chlorobenzene (CB), the PCE of the PBDT-F-TzBI-based device increased to 12.12%. The introduction of the fluorinated benzodithiophene (BDT-F) moiety on the backbone of PBDT-F-TzBI improved the open circuit voltage, short circuit current and fill factor simultaneously. The high PCEs of the PBDT-F-TzBI:ITIC-based devices were supported by comparison and analysis of the optical and electronic properties, the charge carrier mobilities, exciton dissociation probabilities, and charge recombination behaviors of the devices.
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| 3. |
- Bian, Qingzhen, et al.
(författare)
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Reduced Nonradiative Voltage Loss in Terpolymer Solar Cells
- 2020
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 11:10, s. 3796-3802
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Tidskriftsartikel (refereegranskat)abstract
- The dissociation of hybrid local exciton and charge transfer excitons (LE-CT) in efficient bulk-heterojunction nonfullerene solar cells contributes to reduced nonradiative photovoltage loss, a mechanism that still remains unclear. Herein we studied the energetic and entropic contribution in the hybrid LE-CT exciton dissociation in devices based on a conjugated terpolymer. Compared with reference devices based on ternary blends, the terpolymer devices demonstrated a significant reduction in the nonradiative photovoltage loss, regardless of the acceptor molecule, be it fullerene or nonfullerene. Fourier transform photocurrent spectroscopy revealed a significant LE-CT character in the terpolymer-based solar cells. Temperature-dependent hole mobility and photovoltage confirm that entropic and energetic effects contribute to the efficient LE-CT dissociation. The energetic disorder value measured in the fullerene- or nonfullerene-based terpolymer devices suggested that this entropic contribution came from the terpolymer, a signature of higher disorder in copolymers with multiple aromatic groups. This gives new insight into the fundamental physics of efficient LE-CT exciton dissociation with smaller nonradiative recombination loss.
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| 4. |
- Méndez-Reséndiz, Abraham, et al.
(författare)
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Highly crystalline selectively oxidized graphene for supercapacitors
- 2023
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Ingår i: FlatChem. - : Elsevier BV. - 2452-2627. ; 38
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Tidskriftsartikel (refereegranskat)abstract
- Graphene oxide (GO) is usually regarded as a graphene precursor for scalable synthesis, mainly due to its aqueous processability from introducing oxygen functionalities. Nevertheless, the precise control of graphene's oxidation degree to obtain a good balance between dispersion stability and crystallinity remains challenging. This study describes a simple and practical approach to synthesize a new graphene-based material called selectively oxidized graphene (SOG), which combines the advantages of graphene and GO. SOG shows water stability of −36.2 mV, a C/O ratio of 5.2, and most importantly, a very high crystallinity degree, with an ID/IG of 0.414. The synthesized SOG exhibits an ultra-low optical band gap of 0.04 eV, 75 times lower than GO. Moreover, the electrical resistance, 1.12 KΩ/sq is nine orders of magnitude smaller than GO. Additionally, it also shows promising 3-electrode capacitance with an improvement above 400 % compared to exfoliated graphene. A Swagelok-based supercapacitor was fabricated to analyze the feasibility of SOG for energy storage applications, which exhibited remarkable characteristics such as ∼ 93F g−1 capacitance and ∼ 99.8 % retention after 10,000 cycles. The characteristics of SOG ensure that this new material is promising for applications in organic electronics.
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| 5. |
- Mone, Mariza, 1992, et al.
(författare)
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Near-Infrared Emission by Tuned Aggregation of a Porphyrin Compound in a Host–Guest Light-Emitting Electrochemical Cell
- 2021
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Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071 .- 2162-7568. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of 5,10,15,20-tetrakis((5,10-bis((2-hexyldecyl)oxy)dithieno[3,2-c:3′,2′-h][1,5]naphthyridin-2-yl)ethynyl)porphyrin zinc(II) (Por4NT), a near-infrared (NIR) emitting compound, comprising a zinc porphyrin core linked with triple bonds through its meso positions to four 5,10-bis((2-hexyldecyl)oxy)dithieno[3,2-c:3′,2′-h][1,5]naphthyridine (NT) arms is reported. Por4NT featured high solubility in common non-polar solvents, which is ideal for easy processing through solution techniques, and high photoluminescence (PL) efficiency of ≈30% in dilute toluene solution. It also exhibited a strong tendency for aggregation because of its flat conformation, and this aggregation resulted in a strong redshifted emission and a drop in PL efficiency. A well-matched PBDTSi-BDD-Py “host” terpolymer is therefore designed, which is capable of mitigating the aggregation of the Por4NT “guest”. An optimized blend of the host, guest, and an ionic-liquid electrolyte is utilized as the active material in a light-emitting electrochemical cell (LEC), which delivered strong NIR radiance of 134 µW cm-2 with a long wavelength maximum at 810 nm at a low drive voltage of 5.0 V. The attainment of the strong NIR emission from the host–guest LEC is attributed to a tuned aggregation of the Por4NT emitter, which resulted in the desired aggregation-induced redshift of the emission at a reasonably retained efficiency.
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| 6. |
- Mone, Mariza, 1992, et al.
(författare)
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Star-Shaped Diketopyrrolopyrrole-Zinc Porphyrin that Delivers 900 nm Emission in Light-Emitting Electrochemical Cells
- 2019
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 31:23, s. 9721-9728
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Tidskriftsartikel (refereegranskat)abstract
- The development and application of a deep near-infrared (NIR) emitting star-shaped diketopyrrolopyrrole–Zn-porphyrin compound, ZnP(TDPP)4, is reported. The structure, conjugation, and planarity of the porphyrin compound were carefully tuned by molecular design, which resulted in a low-energy photoluminescence peak at 872 nm. The ZnP(TDPP)4 compound was employed as the emissive guest in light-emitting electrochemical cells (LECs), which also comprised the conjugated polymer poly[1,3-bis(2-ethylhexyl)-5-(5-(6-methyl-4,8-bis(5-(tributylsilyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophen-2-yl)thiophen-2-yl)-7-(5-methylthiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione] (PBDTSi-BDD) as the majority host, an ionic liquid as the electrolyte, and two air-stabile electrodes. These systematically optimized host–guest LECs featured a peak electroluminescence at 900 nm, which was delivered at a significant radiance of 36 μW/cm2 and at a low drive voltage of 3.8 V. It is notable that this is the most redshifted NIR emission attained from an LEC device to date, and as such, this work introduces Zn porphyrins as a sustainable and tunable option for emerging emissive NIR applications.
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| 7. |
- Wolkeba, Zewdneh Genene, 1983, et al.
(författare)
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Polymer Acceptors with Flexible Spacers Afford Efficient and Mechanically Robust All-Polymer Solar Cells
- 2022
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 34:6
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Tidskriftsartikel (refereegranskat)abstract
- High efficiency and mechanical robustness are both crucial for the practical applications of all-polymer solar cells (all-PSCs) in stretchable and wearable electronics. In this regard, a series of new polymer acceptors (PAs) is reported by incorporating a flexible conjugation-break spacer (FCBS) to achieve highly efficient and mechanically robust all-PSCs. Incorporation of FCBS affords the effective modulation of the crystallinity and pre-aggregation of the PAs, and achieves the optimal blend morphology with polymer donor (PD), increasing both the photovoltaic and mechanical properties of all-PSCs. In particular, an all-PSC based on PYTS-0.3 PA incorporated with 30% FCBS and PBDB-T PD demonstrates a high power conversion efficiency (PCE) of 14.68% and excellent mechanical stretchability with a crack onset strain (COS) of 21.64% and toughness of 3.86 MJ m-3, which is significantly superior to those of devices with the PA without the FCBS (PYTS-0.0, PCE = 13.01%, and toughness = 2.70 MJ m-3). To date, this COS is the highest value reported for PSCs with PCEs of over 8% without any insulating additives. These results reveal that the introduction of FCBS into the conjugated backbone is a highly feasible strategy to simultaneously improve the PCE and stretchability of PSCs.
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