An inorganic silsesquioxane and organic 4-vinyl biphenyl chromophore based dendrimer was synthesized and the steric
hindrance of the dendrons was used as a trigger to control the photophysical properties in the near-UV and blue spectral
ranges. Consistent photoluminescence quantum yields and time resolved fluorescence were measured in solution,
confirming that molecular engineering of the dendrons together with confinement around the inorganic core allows the
design of more efficient photoluminescent dendrimers. Low temperature photoluminescent studies were completed to
demonstrate the stability of the dendrimer photophysical properties. A very general strategy is then presented which uses
stable chemistry to control the emission spectral range by changing the chromophore, and gives control of
photoluminescence efficiency by grafting side-groups onto the chromophores.
Semiconducting polymers are very promising optoelectronic materials enabling the simple fabrication of devices such as
light-emitting diodes, lasers and solar cells. However, the development of polymer lasers has been hampered by the low
charge mobility of these materials preventing electrically driven lasers. We find that this problem can be overcome by
taking advantage of the complementary properties of inorganic semiconductors. We show that by separating the charge
transporting and lasing regions in a structure combining an indium gallium nitride light-emitting diode with a
semiconducting polymer distributed feedback laser, an electrically pumped hybrid polymer laser can be made. This
provides a new route to simple, convenient, compact and low-cost visible lasers with the potential for applications in
security, sensing, spectroscopy, and medical diagnostics.
Silicon photonics is a rapidly progressing field, where silicon structures are developed
for optical information generation, transmission and processing. Although substantial
progress has been achieved in the fields of transmission and processing,
significant challenges remain to be addressed in generating light on silicon. In this
paper we show that by integrating a silicon resonator with organic semiconductors,
light generation on silicon chips can be achieved in the visible spectral range. Unlike
similar attempts in the telecommunication spectral region, the signal from our device
can be directly measured by silicon photodetectors.
We show that time-resolved luminescence measurements at high excitation densities can be used to study exciton
annihilation and diffusion, and report the results of such measurements on films of P3HT and MEH-PPV. The results fit
to an exciton-exciton annihilation model with a time independent annihilation rate γ, which was measured to be γ =
(2.8±0.5)×10<sup>-8</sup> cm<sup>3</sup>s<sup>-1</sup> in MEH-PPV and γ = (5.2±1)×10<sup>-10</sup> cm<sup>3</sup>s<sup>-1</sup> in P3HT. This implies much faster diffusion in MEHPPV.
Assuming a value of 1 nm for the annihilation radius we evaluated the diffusion length for pristine P3HT in one
direction to be 3.2 nm. Annealing of P3HT was found to increase the annihilation rate to (1.1±0.2)×10<sup>-9</sup> cm<sup>3</sup>s<sup>-1</sup> and the
diffusion length to 4.7 nm.
In this paper we report studies of gain in organic semiconductors, both in solution and the solid-state. OC<sub>1</sub>C<sub>10</sub>-PPV and F8BT solution amplifiers yielded gain of up to 40 dB and on average 30 dB across the spectral range 530-640 nm. We also present a conjugated polymer solid-state amplifier structure, which delivered amplification of 18 dB in a 300 μm channel length. The material used in the solid state amplifier was Dow RedF which had its high gain and low loss properties optimized by blending with F8BT.