Quantum efficiency of ambipolar light-emitting polymer field-effect transistors

Zaumseil, Jana; McNeill, Christopher R.; Bird, Matthew J.; Smith, D. L.; Ruden, P. P.; Roberts, Matthew; McKiernan, Mary J.; Friend, Richard H.; Sirringhaus, Henning

doi:10.1063/1.2894723

Cited by 91 publications

(106 citation statements)

References 35 publications

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“…45 Several studies have indicated that for organic semiconductor materials the EL singlet formation probability is close to 1/4, the quantum-statistical value. [52][53][54][55] However, it has been argued from other studies that it can be strongly enhanced, in particular in polymers. [56][57][58][59][60][61][62][63][64] For poly-phenylene-vinylene (PPV) based polymers, e.g., the singlet fraction as obtained using various methods ranges from approximately 20% (Ref.…”

Section: -mentioning

confidence: 88%

Predictive modeling of the current density and radiative recombination in blue polymer-based light-emitting diodes

Mensfoort

Billen

Carvelli

et al. 2011

Journal of Applied Physics

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The results of a combined experimental and modeling study of charge transport, recombination and light emission in blue organic light-emitting diodes (OLEDs) based on a polyfluorene derivative are presented. It is shown that the measured temperature-dependent current-voltage curves and the voltage-dependent current efficiency are accurately described using an OLED device model that is based on the separately determined unipolar electron and hole mobility functions. The recombination rate is calculated using the Langevin formula, including recombination of holes with free as well as trapped electrons. The light emission is obtained from the exciton formation profile using independently determined values of the exciton radiative decay probability, the average dipole orientation, and assuming a fraction of singlet excitons ηS =(22±3)%, close to the quantum-statistical value. No additional free parameter is used. This shows that predictive one-dimensional device modeling of OLEDs is feasible.

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Section: -mentioning

confidence: 88%

Predictive modeling of the current density and radiative recombination in blue polymer-based light-emitting diodes

Mensfoort

Billen

Carvelli

et al. 2011

Journal of Applied Physics

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“…46 Owing to the relatively large aromatic core of 5, we can expect that both possible products, the major product Br-TBTNidppe-Br 6 and the minor product Br-Nidppe-TBT-Nidppe-Br 7, are formed during the reaction of 5 with NiEt 2 bipy followed by ligand exchange (Scheme 3). Two pairs of doublets with very similar chemical shifts in the 31 P NMR spectrum of the initiator solution point to such a nonequivalent mixture of 6 and 7 (see Figure SI-6). It is important to note that one is still able to determine whether Ni(0)dppe can "ring walk" over the TBT bridge by analyzing the polymeric products.…”

Section: Scheme 1 Mechanism Of F8tbt-br Activation Using Niet 2 Bipymentioning

confidence: 99%

“…3 For example, TBT copolymers with fluorene show ambipolar transport behavior in field-effect transistors 31 and can be used either as p-type 32 or n-type 33 material. In addition, the strong red photoluminescence of conjugated polymers containing TBT units has made such materials interesting candidates for light-emitting devices.…”

mentioning

confidence: 99%

Ring Walking versus Trapping of Nickel(0) during Kumada Catalyst Transfer Polycondensation Using Externally Initiated Electron-Accepting Thiophene–Benzothiadiazole–Thiophene Precursors

et al. 2011

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Interactions of Ni(0) and thiophene–benzothiadiazole–thiophene (TBT) units during the Kumada catalyst transfer polycondensation (KCTP) of 2-chloromagnesio-5-bromo-3-hexylthiophene (1) are investigated. Monofunctional TBT initiator precursors are used for the external initiation of KCTP, and the mechanism of initiator activation and polymerization is elucidated using NMR and MALDI-ToF MS. We find that the activation of the TBT-bromide initiator precursor using nickel–diethylbipyridine (NiEt2bipy) occurs via a two-step pathway, in which NiEt2bipy coordinates to benzothiadiazole (B) first, followed by the elimination of butane and oxidative addition of liberated Ni(0)bipy into the terminal TBT–Br bond. It is shown that the B unit traps Ni(0) during the KCTP of 1, which results in significant termination, as derived from the degree of bromine-terminated chains. The ability of B units to trap Ni(0) is further illustrated by using a symmetric bifunctional Br-TBT-Br initiator precursor for the KCTP of 1, during which Ni(0) is not able to “ring walk” over the B unit to initiate polymerization at the other end of the chain. These results are important for the design of well-defined and electronically end-functionalized conjugated polymers, but also for understanding termination mechanisms in KCTP in general.

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“…[24] An order of magnitude lower electron mobility for F8TBT compared to F8BT is also calculated from transistor characteristics. [25] Given that P3HT:F8TBT blends can achieve reasonable efficiencies despite the relatively poor electron mobility of F8TBT, the origin of the poor efficiency of P3HT:F8BT blends is worth reexamining. Figure 9 presents the device characteristics of 1:1 P3HT:F8BT blends.…”

Section: P3ht:f8bt Blendsmentioning

confidence: 99%

Photophysics and Photocurrent Generation in Polythiophene/Polyfluorene Copolymer Blends

McNeill

Abrusci

Hwang

et al. 2009

Adv Funct Materials

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Here, studies on the evolution of photophysics and device performance with annealing of blends of poly(3‐hexylthiophene) with the two polyfluorene copolymers poly((9,9‐dioctylfluorene)‐2,7‐diyl‐alt‐[4,7‐bis(3‐hexylthien‐5‐yl)‐2,1,3‐benzothiadiazole]‐2′,2′′‐diyl) (F8TBT) and poly(9,9‐dioctylfluorene‐co‐benzothiadiazole) (F8BT) are reported. In blends with F8TBT, P3HT is found to reorganize at low annealing temperatures (100 °C or below), evidenced by a redshift of both absorption and photoluminescence (PL), and by a decrease in PL lifetime. Annealing to 140 °C, however, is found to optimize device performance, accompanied by an increase in PL efficiency and lifetime. Grazing‐incidence small‐angle X‐ray scattering is also performed to study the evolution in film nanomorphology with annealing, with the 140 °C‐annealed film showing enhanced phase separation. It is concluded that reorganization of P3HT alone is not sufficient to optimize device performance but must also be accompanied by a coarsening of the morphology to promote charge separation. The shape of the photocurrent action spectra of P3HT:F8TBT devices is also studied, aided by optical modeling of the absorption spectrum of the blend in a device structure. Changes in the shape of the photocurrent action spectra with annealing are observed, and these are attributed to changes in the relative contribution of each polymer to photocurrent as morphology and polymer conformation evolve. In particular, in as‐spun films from xylene, photocurrent is preferentially generated from ordered P3HT segments attributed to the increased charge separation efficiency in ordered P3HT compared to disordered P3HT. For optimized devices, photocurrent is efficiently generated from both P3HT and F8TBT. In contrast to blends with F8TBT, P3HT is only found to reorganize in blends with F8BT at annealing temperatures of over 200 °C. The low efficiency of the P3HT:F8BT system can then be attributed to poor charge generation and separation efficiencies that result from the failure of P3HT to reorganize.

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Quantum efficiency of ambipolar light-emitting polymer field-effect transistors

Cited by 91 publications

References 35 publications

Predictive modeling of the current density and radiative recombination in blue polymer-based light-emitting diodes

Predictive modeling of the current density and radiative recombination in blue polymer-based light-emitting diodes

Ring Walking versus Trapping of Nickel(0) during Kumada Catalyst Transfer Polycondensation Using Externally Initiated Electron-Accepting Thiophene–Benzothiadiazole–Thiophene Precursors

Photophysics and Photocurrent Generation in Polythiophene/Polyfluorene Copolymer Blends

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