| 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
-
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. |
- Benavides, Cindy Montenegro, et al.
(författare)
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High-Performance Organic Photodetectors from a High-Bandgap Indacenodithiophene-Based π-Conjugated Donor-Acceptor Polymer
- 2018
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 10:15, s. 12937-12946
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Tidskriftsartikel (refereegranskat)abstract
- A conjugated donor-acceptor polymer, poly[4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl-alt-5-(2-ethylhexyl)-4H-thieno[3,4-c] pyrrole-4,6(5H)-dione-1,3-diyl] (PIDT-TPD), is blended with the fullerene derivative [6,6] phenyl-C61-butyric acid methyl ester (PC 61 BM) for the fabrication of thin and solution-processed organic photodetectors (OPDs). Systematic screening of the concentration ratio of the blend and the molecular weight of the polymer is performed to optimize the active layer morphology and the OPD performance. The device comprising a medium molecular weight polymer (27.0 kg/mol) in a PIDT-TPD:PC 61 BM 1:1 ratio exhibits an external quantum efficiency of 52% at 610 nm, a dark current density of 1 nA/cm 2 , a detectivity of 1.44 × 10 13 Jones, and a maximum 3 dB cutoff frequency of 100 kHz at -5 V bias. These results are remarkable among the state-of-the-art red photodetectors based on conjugated polymers. As such, this work presents a functional organic active material for high-speed OPDs with a linear photoresponse at different light intensities.
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| 3. |
- Murto, Petri Henrik, 1984, et al.
(författare)
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High performance all-polymer photodetector comprising a donor-Acceptor-Acceptor structured indacenodithiophene-bithieno[3,4-c] pyrroletetrone copolymer
- 2018
-
Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 7:4, s. 395-400
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of an acceptor polymer PIDT-2TPD, comprising indacenodithiophene (IDT) as the electron-rich unit and an interconnected bithieno[3,4-c]pyrrole-4,4′,6,6′-Tetrone (2TPD) as the electron-deficient unit, and its application for all-polymer photodetectors is reported. The optical, electrochemical, charge transport, and device properties of a blend of poly(3-hexylthiophene) and PIDT-2TPD are studied. The blend shows strong complementary absorption and balanced electron and hole mobility, which are desired properties for a photoactive layer. The device exhibits dark current density in the order of 10 -5 mA/cm 2 , external quantum efficiency broadly above 30%, and nearly planar detectivity over the entire visible spectral range (maximum of 1.1 × 10 12 Jones at 610 nm) under-5 V bias. These results indicate that PIDT-2TPD is a highly functional new type of acceptor and further motivate the use of 2TPD as a building block for other n-Type materials.
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| 4. |
- Murto, Petri Henrik, 1984, et al.
(författare)
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Incorporation of Designed Donor−Acceptor−Donor Segments in a Host Polymer for Strong Near-Infrared Emission from a Large-Area Light-Emitting Electrochemical Cell
- 2018
-
Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 1:4, s. 1753-1761
-
Tidskriftsartikel (refereegranskat)abstract
- Cost-efficient thin-film devices that emit in the nearinfrared (NIR) range promise a wide range of important applications. Here, the synthesis and NIR application of a series of copolymers comprising poly[indacenodithieno[3,2- b ]thiophene-2,8-diyl] (PIDTT) as the host and different donor−acceptor−donor (DAD) segments as the guest are reported. We find that a key design criterion for efficient solid-state host-to-guest energy transfer is that the DAD conformation is compatible with the conformation of the host. Such host−guest copolymers are evaluated as the emitter in light-emitting electrochemical cells (LECs) and organic light-emitting diodes, and the best performance is invariably attained from the LEC devices because of the observed balanced electrochemical doping that alleviates issues with a noncentered emission zone. An LEC device comprising a host−guest copolymer with 4,4-bis(2-ethylhexyl)-4 H -silolo[3,2- b :4,5- b′ ]dithiophene as the donor and benzo[ c ][1,2,5]thiadiazole as the acceptor delivers an impressive near-infrared (NIR) performance in the form of a high radiance of 1458 μ W/cm2 at a peak wavelength of 725 nm when driven by a current density of 500 mA/cm2, a second-fast turn-on, and a good stress stability as manifested in a constant radiance output during 3 days of uninterrupted operation. The high-molecular-weight copolymer features excellent processability, and the potential for low-cost and scalable NIR applications is verified through a spray-coating fabrication of a >40 cm2 large-area device, which emits intense and uniform NIR light at a low drive voltage of 4.5 V.
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| 5. |
- Murto, Petri Henrik, 1984, et al.
(författare)
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Triazolobenzothiadiazole-Based Copolymers for Polymer Light-Emitting Diodes: Pure Near-Infrared Emission via Optimized Energy and Charge Transfer
- 2016
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Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071. ; 4:12, s. 2068-2076
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.A series of new near-infrared (NIR) emitting copolymers, based on a low band gap 6-(2-butyloctyl)-4,8-di(thiophen-2-yl)-[1,2,3]triazolo[4',5':4,5]benzo[1,2-c]-[1,2,5]thiadiazole (TBTTT) fluorophore copolymerized into a high band gap poly[3,3'-ditetradecyl-2,2'-bithiophene-5,5'-diyl-alt-5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl] (P2TTPD) host backbone, for polymer light-emitting diode (PLED) applications is reported. PLEDs fabricated from the host polymer (P2TTPD-0) show external quantum efficiencies (EQEs) up to 0.49% at 690 nm, with turn-on voltage (Von) at only 2.4 V. By incorporating the TBTTT segments into the host polymer backbone, pure NIR emission peaking at ca. 900 nm is obtained with Von remaining below 5 V. This work demonstrates that such a low Von can be attributed to efficient intrachain energy and/or charge transfer to the TBTTT sites. When the NIR emitting copolymer (P2TTPD-10) is blended with P2TTPD-0, the TBTTT are confined to well-separated polymer chains. As a result, the EQE from the blend is lower and the Von higher than that obtained from the pure copolymer (P2TTPD-1.0) with equal content of TBTTT. An analogous copolymer (P4T-1.0), consisting of poly[3,3'-ditetradecyl-2,2':5',2'':5'',2'''-quaterthiophene-5,5'''-diyl] (P4T) as the host and 1% TBTTT as the NIR emitter, further demonstrates that pure NIR emission can be obtained only through optimized molecular orbital energy levels, as in P2TTPD-1.0, which minimizes chances for either charge trapping or exciton splitting.
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| 6. |
- Tang, Shi, et al.
(författare)
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Intense and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells Comprising a Metal-Free Indacenodithieno[3,2-b]thiophene-Based Copolymer as the Single Emitter
- 2017
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 29:18, s. 7750-7759
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis, characterization, and application of a series of metal-free near-infrared (NIR) emitting alternating donor/acceptor copolymers based on indacenodithieno[3,2-b]thiophene (IDTT) as the donor unit. A light-emitting electrochemical cell (LEC), comprising a blend of the copolymer poly[indacenodithieno[3,2-b]thiophene-2,8-diyl-alt-2,3-diphenyl-5,8-di(thiophen-2-y1)- quinoxaline-5,5'-diy1] and an ionic liquid as the single-layer active material sandwiched between two air-stable electrodes, delivered NIR emission (lambda(peak) = 705 nm) with a high radiance of 129 mu W/cm(2) when driven by a low voltage of 3.4 V. The NIR-LEC also featured good stress stability, as manifested in that the peak NIR output from a nonencapsulated device after 24 h of continuous operation only had dropped by 3% under N-2 atmosphere and by 27% under ambient air. This work accordingly introduces IDTT-based donor/acceptor copolymers as functional metal-free electroluminescent materials in NIR-emitting devices and also provides guidelines for how future NIR emitters should be designed for further improved performance.
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| 7. |
- Bini, Kim, 1987, et al.
(författare)
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Broad spectrum absorption and low-voltage electrochromic operation from indacenodithieno[3,2-: B] thiophene-based copolymers
- 2019
-
Ingår i: Polymer Chemistry. - : Royal Society of Chemistry (RSC). - 1759-9954 .- 1759-9962. ; 10:16, s. 2004-2014
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Tidskriftsartikel (refereegranskat)abstract
- Electrochromic performance of conjugated polymers has quickly become an important design factor in a variety of applications. There is still significant need to develop highly stable materials with high optical contrast, desired colour switching and fast kinetics. Here, poly[indacenodithieno[3,2-b]thiophene-2,8-diyl] (PIDTT) is introduced as a new type of electrochromic polymer exhibiting a narrow absorption band, excellent electrochemical stability and fast colour switching kinetics between vibrant red (peak maximum at ∼550 nm) and transparent (peak maximum at ∼920 nm) within a low potential range of 0-0.8 V. To widen the spectral coverage of the well-functioning PIDTT over the entire visible range, a modified donor-acceptor approach is used by incorporating three different donor-acceptor-donor (DAD) segments into an indacenodithieno[3,2-b]thiophene (IDTT) based polymer backbone, so as to obtain three different alternating copolymers. This design motif is further rationalized by the maintained electrochemical stability of the new copolymers, and their full colour switching between black and transparent down to an ultra-low potential range of 0-0.6 V.
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| 8. |
- Chvojka, Petr, et al.
(författare)
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Expanded Multiband Super-Nyquist CAP Modulation for Highly Bandlimited Organic Visible Light Communications
- 2020
-
Ingår i: IEEE Systems Journal. - 1932-8184 .- 1937-9234. ; 14:2, s. 2544-2550
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we experimentally demonstrate a novel expanded nonorthogonal multiband super-Nyquist carrier-less amplitude and phase (m-ESCAP) modulation for bandlimited organic visible light communication (VLC) systems. The proposed scheme has the same bandwidth requirement as the conventional m-CAP while breaking the orthogonality between subcarriers by purposely overlapping them. We compare m-ESCAP with the conventional m-CAP and a compressed nonorthogonal version of m-CAP (m-SCAP) in terms of measured bit error rate (BER) performance, bit rates, and spectral efficiencies. We show that the m-ESCAP system offers improvement in the bit rate of $\sim$10% and 20% compared to the m-CAP and m-SCAP, respectively, and in the spectral efficiency of $\sim$20% compared to m-CAP. These gains are achieved at the cost of increased BER, which, however, remains below the 7% forward error correction limit.
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| 9. |
- Haigh, Paul Anthony, et al.
(författare)
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Experimental demonstration of staggered cap modulation for low bandwidth red-emitting polymer-LED based visible light communications
- 2019
-
Ingår i: 2019 IEEE International Conference on Communications Workshops, ICC Workshops 2019 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- © 2019 IEEE. In this paper we experimentally demonstrate, for the first time, staggered carrier-less amplitude and phase (sCAP) modulation for visible light communication systems based on polymer light-emitting diodes emitting at ∼639 nm. The key advantage offered by sCAP in comparison to conventional multiband CAP is its full use of the available spectrum. In this work, we compare sCAP, which utilises four orthogonal filters to generate the signal, with a conventional 4-band multi-CAP system and on-off keying (OOK). We transmit each modulation format with equal energy and present a record un-coded transmission speed of ∼6 Mb/s. This represents gains of 25% and 65% over the achievable rate using 4-CAP and OOK, respectively.
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| 10. |
- Haigh, Paul Anthony, et al.
(författare)
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Hybrid Super-Nyquist CAP Modulation based VLC with Low Bandwidth Polymer LEDs
- 2019
-
Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC. ; 2019-September
-
Konferensbidrag (refereegranskat)abstract
- Visible light communication systems often suffer from high frequency attenuation when transmitting out-of-band. This effect has been ameliorated by multi-band modulations such as multi-band carrier-less amplitude and phase (m-CAP), which minimises the effect of decreased high frequency magnitude and maximises signal-to-noise ratio-per-sub-band. On the other hand, in the pass-band region, super-Nyquist CAP (SCAP) can offer throughput improvements with no additional complexity at the receiver, at the cost of bit error rate. We propose, for the first time, a new hybrid SCAP modulation format that takes advantageous of both SCAP (i.e. overlapped sub-bands within the modulation bandwidth) and conventional m-CAP (orthogonally spaced bands outside the modulation bandwidth) while maintaining isolation between noise sources. We show higher baud rates within the passband region whilst supporting out-of-band transmission at lower error vector magnitudes.
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| 11. |
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| 12. |
- Minotto, Alessandro, et al.
(författare)
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Efficient Near-Infrared Electroluminescence at 840 nm with “Metal-Free” Small-Molecule:Polymer Blends
- 2018
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 30:34
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the so-called energy-gap law and aggregation quenching, the efficiency of organic light-emitting diodes (OLEDs) emitting above 800 nm is significantly lower than that of visible ones. Successful exploitation of triplet emission in phosphorescent materials containing heavy metals has been reported, with OLEDs achieving remarkable external quantum efficiencies (EQEs) up to 3.8% (peak wavelength > 800 nm). For OLEDs incorporating fluorescent materials free from heavy or toxic metals, however, we are not aware of any report of EQEs over 1% (again for emission peaking at wavelengths > 800 nm), even for devices leveraging thermally activated delayed fluorescence (TADF). Here, the development of polymer light-emitting diodes (PLEDs) peaking at 840 nm and exhibiting unprecedented EQEs (in excess of 1.15%) and turn-on voltages as low as 1.7 V is reported. These incorporate a novel triazolobenzothiadiazole-based emitter and a novel indacenodithiophene-based transport polymer matrix, affording excellent spectral and transport properties. To the best of knowledge, such values are the best ever reported for electroluminescence at 840 nm with a purely organic and solution-processed active layer, not leveraging triplet-assisted emission.
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| 13. |
- Mone, Mariza, 1992, et al.
(författare)
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Low-gap zinc porphyrin as an efficient dopant for photomultiplication type photodetectors
- 2020
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1364-548X .- 1359-7345. ; 56:84, s. 12769-12772
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Tidskriftsartikel (refereegranskat)abstract
- A new zinc porphyrin, named as Por4IC, was synthesized, which through extension of conjugation and an enhancement of planarity and donor-acceptor interactions exhibits a very low band gap. The molecule was able to efficiently facilitate a photomultiplication effect in blend with P3HT which was assisted by electron trapping followed by hole tunneling injection from the Al electrode giving rise to a high external quantum efficiency of 22 182% and a specific detectivity of 4.4 × 1012 Jones at 355 nm and at -15 V bias. This work introduces porphyrin derivatives as promising dopants for photomultiplication type photodetectors. This journal is
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| 14. |
- 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
-
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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| 15. |
- 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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| 16. |
- Murto, Petri Henrik, 1984, et al.
(författare)
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Highly Stable Indacenodithieno[3,2-b]thiophene-Based Donor-Acceptor Copolymers for Hybrid Electrochromic and Energy Storage Applications
- 2020
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 1520-5835 .- 0024-9297. ; 53:24, s. 11106-11119
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Tidskriftsartikel (refereegranskat)abstract
- Stable doping of indacenodithieno[3,2-b]thiophene (IDTT) structures enables easy color tuning and significant improvement in the charge storage capacity of electrochromic polymers, making use of their full potential as electrochromic supercapacitors and in other emerging hybrid applications. Here, the IDTT structure is copolymerized with four different donor-acceptor-donor (DAD) units, with subtle changes in their electron-donating and electron-withdrawing characters, so as to obtain four different donor-acceptor copolymers. The polymers attain important form factor requirements for electrochromic supercapacitors: desired switching between achromatic black and transparent states (L*a*b∗ 45.9, -3.1, -4.2/86.7, -2.2, and -2.7 for PIDTT-TBT), high optical contrast (72% for PIDTT-TBzT), and excellent electrochemical redox stability (Ired/Iox ca. 1.0 for PIDTT-EBE). Poly[indacenodithieno[3,2-b]thiophene-2,8-diyl-alt-4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-(2-hexyldecyl)-2H-benzo[d][1,2,3]triazole-7,7′-diyl] (PIDTT-EBzE) stands out as delivering simultaneously a high contrast (69%) and doping level (>100%) and specific capacitance (260 F g-1). This work introduces IDTT-based polymers as bifunctional electro-optical materials for potential use in color-tailored, color-indicating, and self-regulating smart energy systems.
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| 17. |
- Murto, Petri Henrik, 1984
(författare)
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Synthesis of Conjugated Polymers and Small Molecules for Organic Light-Emitting Devices and Photodetectors
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Production cost and environmental impact are the two major concerns that are related to the conventional optoelectronic devices. It is desirable for the modern semiconductors that they are free of toxic/costly metals, they can be processed with low-cost solution-based methods, and their optical, electronic, and mechanical properties can be easily tuned depending on the target application. In this thesis, a range of different conjugated polymers and small molecules are designed and synthesized as semiconductors for organic light-emitting diodes (OLEDs), light-emitting electrochemical cells (LECs), and organic photodetectors (OPDs). In organic light-emitting devices, the emissive molecule is commonly mixed with a charge transporting host matrix, which can be either a small molecule or a conjugated polymer. The latter is beneficial since it does not require deposition of the emitter and matrix components in high vacuum and high temperature conditions. The polymeric materials can be dissolved and printed on a substrate of any desired size and production scale, at room temperature, and even under ambient air. The specific wavelength range of near-infrared (NIR) at λ >700 nm is of interest for a wide range of applications spanning from optical communication to biosensing. However, the low energy of NIR range poses challenges for the materials design, in terms of emission efficiency and light intensity, which are further addressed in this thesis, allowing the fabrication of high-performance NIR-OLEDs and NIR-LECs. For photodetectors, absorption of a wide spectrum of light is beneficial in biosensing and imaging applications. Low noise and fast charge extraction are necessary for the detection of light at high speeds even at low intensities. These aspects are studied in this thesis by designing new polymers with different absorption, charge transport, and morphological properties in the photoactive layer. Two polymers enabled the fabrication of visible (red) OPDs with a low dark current (the main constituent in the noise), high detectivity, and high photoresponse speed.
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| 18. |
- Tang, Shi, et al.
(författare)
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On the Design of Host-Guest Light-Emitting Electrochemical Cells : Should the Guest be Physically Blended or Chemically Incorporated into the Host for Efficient Emission?
- 2019
-
Ingår i: Advanced Optical Materials. - : Wiley-VCH Verlagsgesellschaft. - 2162-7568 .- 2195-1071. ; 7:18
-
Tidskriftsartikel (refereegranskat)abstract
- It has recently been demonstrated that light-emitting electrochemical cells (LECs) can be designed to deliver strong emission with high efficiency when the charge transport is effectuated by a majority host and the emission is executed by a minority guest. A relevant question is then: should the guest be physically blended with or chemically incorporated into the host? A systematic study is presented that establishes that for near-infrared-(NIR-) emitting LECs based on poly(indacenodithieno[3,2-b]thiophene) (PIDTT) as the host and 4,7-bis(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b ']dithiophen-2-yl)benzo[c][1,2,5]-thiadiazole (SBS) as the guest the chemical-incorporation approach is preferable. The host-to-guest energy transfer in LEC devices is highly efficient at a low guest concentration of 0.5%, whereas guest aggregation and ion redistribution during device operation severly inhibits this transfer in the physical-blend devices. The chemical-incorporation approach also results in a redshifted emission with a somewhat lowered photoluminescence quantum yield, but the LEC performance is nevertheless very good. Specifically, an NIR-LEC device comprising a guest-dilute (0.5 molar%) PIDTT-SBS copolymer delivers highly stabile operation at a high radiance of 263 mu W cm(-2) (peak wavelength = 725 nm) and with an external quantum efficiency of 0.214%, which is close to the theoretical limit for this particular emitter and device geometry.
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| 19. |
- Tejerina, Lara, et al.
(författare)
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A porphyrin pentamer as a bright emitter for NIR OLEDs
- 2022
-
Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7534 .- 2050-7526. ; 10:15, s. 5929-5933
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Tidskriftsartikel (refereegranskat)abstract
- The Luminescence and electroluminescence of an ethyne-Linked zinc(II) porphyrin pentamer have been investigated, by testing blends in two different conjugated polymer matrices, at a range of concentrations. The best results were obtained for blends with the conjugated polymer PIDT-2TPD, at a porphyrin loading of 1 wt%. This host matrix was selected because the excellent overlap between its emission spectrum and the low-energy region of the absorption spectrum of the porphyrin oligomer leads to efficient energy transfer. Thin films of this blend exhibit intense fluorescence in the near-infrared (NIR), with a peak emission wavelength of 886 nm and a photoluminescent quantum yield (PLQY) of 27% in the solid state. Light-emitting diodes (LEDs) fabricated with this blend as the emissive layer achieve average external quantum efficiencies (EQE) of 2.0% with peak emission at 830 nm and a turn-on voltage of 1.6 V. This performance is remarkable for a singlet NIR-emitter; 93% of the photons are emitted in the NIR (lambda > 700 nm), indicating that conjugated porphyrin oligomers are promising emitters for non-toxic NIR OLEDs.
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| 20. |
- Xiong, Wenjing, 1989, et al.
(författare)
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Combining Benzotriazole and Benzodithiophene Host Units in Host-Guest Polymers for Efficient and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells
- 2019
-
Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071 .- 2162-7568. ; 7:15
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Tidskriftsartikel (refereegranskat)abstract
- A set of host-guest copolymers with alternating benzodithiophene and benzotriazole (BTz) derivatives as host units and 4,7-bis(5-bromothiophen-2-yl)-benzo[c][1,2,5]thiadiazole as the minority guest are synthesized, characterized, and evaluated for applications. A light-emitting electrochemical cell (LEC) comprising such a host-guest copolymer delivers fast-response near-infrared (NIR) emission peaked at 723 nm with a high radiance of 169 mu W cm(-2) at a low drive voltage of 3.6 V. The NIR-LEC also features good stability, as the peak NIR output only drops by 8% after 350 h of continuous operation. It is, however, found that the LEC performance is highly sensitive to the detailed chemical structure of the host backbone, and that the addition of electron-donating thiophene bridging units onto the BTz unit is highly positive while the inclusion of fluorine atoms results in a drastically lowered performance, presumably because of the emergence of hydrogen bonding within the active material.
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