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

Abstract

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 pi-electron system to pi-electron system interactions that quench exciton luminescence. 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 (mu approximately 3-6 x 10(-2) cm2 V-1 s-1) and simultaneously excellent light-emission characteristics. These materials are expected to be of interest for light-emitting transistors, light-emitting diode sources for optical communications and may offer renewed hope for electrically pumped laser action. 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 microJ cm-2) for 10 Hz, 12 ns, 390 nm excitation) and slope efficiencies (up to 11%).

Monodisperse conjugated polymer particles by Suzuki–Miyaura dispersion polymerization

“…1c. The fluorescence spectra of conjugated polymer particle dispersions P1, P2 and P4 closely resemble those of solid films of the same conjugated polymers, prepared via hetero-phase Suzuki polymerization [25][26][27] .…”

Advances in small lasers

“…In addition, their large conjugated π-electron systems confer semiconducting properties, opening up the prospect of direct current injection although the low charge carrier mobility of organic semiconductors has so far prevented lasing through direct electrical pumping in these materials. Strategies to obtain materials with improved charge mobility and high optical gain involve fine-tuning the conjugated backbone of polymeric materials or introducing long-range order 43,44 . Optically pumped organic semiconductor laser configurations have been explored in considerable detail.…”

Analytical study of vertical external-cavity surface-emitting organic lasers

“…In the perspective of having compact organic laser sources which integrate the pump and the laser cavity in a small-volume device, there have been several achievements through indirect electrical pumping of organic solid-state lasers via Light Emitting Diodes [13] or nitride diode lasers [14,15] by means of somehow sophisticated electronic circuitry systems for the pump source to make it operate in a pulsed regime. This indirect excitation approach has been chosen since realization of direct electrically-pumped organic semiconductor laser is hindered by several heavy constraints like low charge-carrier mobility of organic semiconductor materials as well as several loss mechanisms such as electrode losses and polaronic absorption [16][17][18]. Therefore, optically-pumped organic semiconductor lasers are of foremost importance.…”