Simultaneous optimization of charge-carrier mobility and optical gain in semiconducting polymer films

The Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.
Nature Material (Impact Factor: 36.5). 06/2008; 7(5):376-80. DOI: 10.1038/nmat2165
Source: PubMed


The combination of efficient light emission and high charge-carrier mobility has thus far proved elusive for polymer semiconductors, with high mobility typically achieved by cofacial -electron system to -electron system interactions that quench exciton luminescence1, 2. We report a new strategy, comprising the introduction of a limited number of more effective hopping sites between otherwise relatively isolated, and thus highly luminescent, polyfluorene chains. Our approach results in polymer films with large mobility (3–610-
2 cm2 V-
1 s-
1) and simultaneously excellent light-emission characteristics. These materials are expected to be of interest for light-emitting transistors3, light-emitting diode sources for optical communications4 and may offer renewed hope for electrically pumped laser action2, 5, 6. In the last context, optically pumped distributed feedback lasers comprising one-dimensional etched silica grating structures coated with polymer have state-of-the-art excitation thresholds (as low as 30 W cm-
2 (0.1 nJ per pulse or 0.3 J cm-
2) for 10 Hz, 12 ns, 390 nm excitation) and slope efficiencies (up to 11%

Download full-text


Available from: Mariano Campoy-Quiles,

Click to see the full-text of:

Article: Simultaneous optimization of charge-carrier mobility and optical gain in semiconducting polymer films

0 B

See full-text
  • Source
    • "The most straight-forward way to eliminate concentration quenching is blending molecules with polymer host material. Unfortunately, diluting the material significantly reduces charge carrier mobility [14], and moreover adversely affects organic laser efficiency [8]. Nonetheless, this method is advantageous for determining the relation between ASE threshold and the molecular concentration in the low-loss waveguiding films. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The impact of linking topology of fluorene-carbazole triads on amplified and spontaneous emission as well as on concentration quenching of emission and charge carrier mobility, i.e. on the properties essential for organic laser application, was investigated. Deep-blue-emitting triads featuring 2,7- substitution pattern and bulky alkyl moieties expressed high emission quantum yield (0.8-0.9) and low concentration quenching, which benefited in attaining large radiative decay rates (∼109 s-1) and rather low amplified spontaneous emission (ASE) threshold (down to 9 kW/cm2) for compound concentrations up to 3 wt % in polymer matrix. Most of the triads expressed carrier drift mobilities close to 10-2 cm2/(V·s) in amorphous films pointing out efficient charge transport essential for reducing threshold current density for lasing. The impact of the position (central or side) of fluorene/carbazole moieties in the triad or the linking position (C-2 or C-3) of the side groups on the ASE threshold and carrier mobility was found to be of little significance. However, a huge advantage of 2,7- substitution pattern over 3,6- pattern for the triads in terms of ASE performance was demonstrated. Importantly, the obtained results suggested a possible trade-off between ASE threshold reduction and carrier mobility enhancement, which may hamper the realization of electrically-driven lasing in organic amorphous films.
    Dyes and Pigments 08/2015; 123. DOI:10.1016/j.dyepig.2015.08.019 · 3.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Dit proefschrift handelt over het ontwerp van nieuwe architectuur- en materiaalconcepten voor organische licht-emitterende structuren. Daarbij wordt vooral aandacht besteed aan het behalen van hoge stroomdichtheden en een goede controle van de tripletconcentratie. Een nieuwe licht-emitterende structuur, een OLED met veld-effect electronentransport, wordt voorgesteld. Deze structuur is een hybride tussen een diode en een veld-effect transistor. In vergelijking met conventionele OLEDs is het metallisch top-contact op een afstand van verschillende micrometers van de actieve laag van de diode geplaatst. Door deze relatief grote afstand tussen het metallisch contact en de actieve laag, kunnen de optische absorptieverliezen beperkt worden voor licht dat lateraal in de structuur geleid wordt. De geïnjecteerde elektronen verzamelen zich aan een organische heterojunctie en verplaatsten zich tot de actieve laag onder invloed van het veld-effect. Op deze manier worden hoge ladingsdragersmobiliteiten behaald in de structuur, wat een hoge stroomdichtheid en een vermindering van het aantal ladingsdragers met zich meebrengt. Experimenten onder gepulste excitatie tonen aan dat pulsen met een pulsbreedte tot 1 µs aangelegd kunnen worden aan de structuur zonder dat de lichtintensiteit afneemt. Dit zou het mogelijk moeten maken om de opeenhoping van triplets tegen te gaan. De combinatie van al deze eigenschappen maakt deze OLED met veld-effect electronentransport een zeer interessante structuur voor golfgeleidende OLEDs en toekomstige elektrisch gepompte lasers. Bovendien, worden ook triplet-gedopeerde organische materialen en het gebruik van `triplet scavengers' in geconjugeerde polymeren onderzocht. This thesis focuses on the design of new device and material concepts for organic light-emitting devices, thereby targeting high current densities and an improved control of the triplet concentration. A new light-emitting device architecture, the OLED with field-effect electron transport, is demonstrated. This device is a hybrid between a diode and a field-effect transistor. Compared to conventional OLEDs, the metallic cathode is displaced by one to several micrometers from the light-emitting zone, reducing optical absorption losses. The electrons injected by the cathode accumulate at an organic heterojunction and are transported to the light-emission zone by field-effect. High mobilities for charge carriers are achieved in this way, enabling a high current density and a reduced number of charge carriers in the device. Pulsed excitation experiments show that pulses up to 1 µs can be applied to this structure without affecting the light intensity, suggesting that pulsed excitation might be useful to reduce the accumulation of triplets in the device. The combination of all these properties make the OLED with field-effect electron transport particularly interesting for waveguide devices and future electrically pumped lasers. In addition, triplet-emitter doped organic materials as well as the use of triplet scavengers in conjugated polymers are investigated. Doctor in de ingenieurswetenschappen Geassocieerde Afdeling ESAT - INSYS Departement Elektrotechniek (ESAT) Faculteit Ingenieurswetenschappen Doctoral thesis Doctoraatsthesis

Show more