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Photonic and Opto-electronic polymers

Photonic and Opto-electronic polymers

Optoelectronic conjugated polymers for plastic solar cells and organic light emitting diodes;

A1. Polymer photovoltaics

The development of renewable sources of energy is a global major issue, photovoltaic energy conversion appears as a promising alternative to fossil energy based on its non-toxic and non-polluting operation, as well as on an inexhaustible resource. However, although silicon based solar cells exhibit some of the highest power conversion efficiency (up to 24%), their high production cost caused by energy intensive processing techniques, limit their widespread applications in the future. In this context, organic conjugated polymer based solar cells take advantage of low-cost, large area, solution-based manufacturing via spin coating, ink-jet printing and screen printing, and allowing the development of applications on flexible substrates.

Our project will address material synthesis, thin film structure of the active layers and fabrication of devices with the overall aim of improving the efficiency and reducing costs of large-area/large scale production of polymer based solar cells. We will focus on three important aspects: a.) novel n-type conjugated polymers and triplet materials; b.) nanostructured thin films as active layers where the nanostructure is controlled by nanocrystals and/or self-assembly from conjugated oliogmers/polymers; c.) controlled fabrication of devices using roll-to-roll processing such that the correct structure is achieved in finally processed devices. We aim at:

  • N-type conjugated oligomers/polymers
  • Polymer nanowires from template syntheses of silica scaffolds
  • Low band-gap polymers
  • D-A di-, tri-block copolymers and their self-assembly
  • Thermo-stability of the active layers
  • Triplet materials for high PCE
  • Donor-acceptor polymers with conjugated pendants
  • Screen printing and R2R printing for fabrication of all plastic solar cells

A2. Organic light emitting diodes (OLEDs)

Organic polymers emitting lights under an electric field have commanded increasing attention since the last two decades both for their scientific interests and their applications such as the fabrication of flat large-area thin film displays at reduced cost, flexible monitors. Our project is to develop a novel self-assembling approach for poly(p-phenylene vinylene) derivatives from the viewpoint of molecular architecture, followed by anodic coupling in the interface between polymer layers and chemical modified ITO in order to create a crosslinking structure of the EL polymers. Therefore great improvement of both transportations of the carriers, the quantum efficiency and themo-stability of the LED device will be expected. Our main tasks are:

  • Syntheses of PPV derivatives
  • Surface modification of ITO
  • Self-assembly of conjugated polymers and in-situ anodic coupling at the interface
  • N-IR/IR emission (from PL to EL)
  • White light emitter
  • Screen printing of OLED indicators

A3. Insulated molecular wires from cyclodextrin based polyrotaxanes

Conjugated polymers, recognized as molecular wires and based on their possible high electronic conductivity along individual polymer chains, have been widely studied and commercially produced for their applications in light-emitting diodes, field-effect transistors and photovoltaic devices, and have shown great importance for their potential applicability as next generation mono-molecular electronic devices. However, their strong intermolecular forces results in disadvantages in their optical properties such as broadening the absorption/emission spectra and quenching the fluorescence. This can be overcome by formation of insulated molecular wires (IMWs) composed of encapsulated conjugated polymers by hydrophobic hosts, e.g., cyclodextrin based polyrotaxanes. Our work covers:

  • Syntheses and characterization of pre-coupling complexes between cyclodextrin and conjugated monomers
  • Controlled coupling reactions
  • Self-assembly of the IMWs on ITO surface
  • Property testing of the device