New “High-Tech” Organic Materials for using as active layers in organic electronic devices Organic electronic or plastic electronic are the applications of electrically-conductive polymers and conductive small molecules as semiconductors in electronic circuit or substrate for electronic devices. These organic semiconductors are lighter, more flexible, and less expensive than inorganic conductors. This makes them a desirable alternative in many applications. It also creates the possibility of new applications that would be impossible using copper or silicon. New applications include smart windows and electronic paper. The most interesting electronic devices include organic light-emitting diodes (OLED), organic solar cell (OSC) and organic field effect transistor (OFET).
Organic light-emitting diode (OLED) is a diode that uses thin film of organic molecules to emit light when applied with voltage. The emission colors can be varied by tuning on the molecular structures of the organic emitter. At present, this technology has been used as a display of the many kinds of electronic devices that are both beautiful and energy-saving such as mobile phone and camera screens. The main aim of our research in this topic is to develop new materials for OLED, particularly white OLED (WOLED) for lighting application.
Benefit of OLED in lighting applications
Numbers of small molecules and dendrimers with a combine light-emitting and hole-transporting properties were studied as non-doped solution processed materials in organic light-emitting diodes (OLED).
Examples are a series of bis(3,6-di-tert-butylcarbazol-9-ylphenyl)aniline end-capped oligoarylenes (BCPA-Ar). The optical properties can be easily fine-tuned by either varying the degree of π-conjugation or using electron affinities of the aryl cores. As a result, their emission spectra can cover the full UV−vis spectrum (426−644 nm). Remarkably, solution-processed nondoped BCPA-Ars-based OLEDs show moderate to excellent device performance with emission colors spanning
the whole visible spectrum (deep blue to red).
Carbazole dendrimers containing bifluorene, bis(fluoren-2-yl)benzothiadiazole and bis[-5-(fluoren-2-yl)thiophen-2-yl]benzothiadiazole as fluorescent cores display a bright RGB fluorescence and can form morphologically stable amorphous thin films with glass transition temperatures. Simple structured solution-processed WOLEDs using a mixture of these dendrimers as an emitter emit stable white (CIE = 0.33, 0.35) with high luminance efficiency.
Applications for OLED lighting?
Fig. OLED photos.
Organic Solar Cells (OSC) is a type of polymer solar cell that uses conductive organic polymers or small organic molecules for light absorption and charge transport to produce electricity from sunlight by the photovoltaic effect such as dye-sensitized solar cell (DSSC) and bulk heterojunction Solar cell (BHJSC). The organic material used in organic solar cells has low production costs in high volumes. Combined with the flexibility of organic molecules, OSC are potentially cost-effective for photovoltaic applications. The main disadvantages associated with OSC are low efficiency, low stability and low strength compared to inorganic photovoltaic cell. However, this can be improved. The main aim of our research in this topic is to develop new materials for highly efficient OSC.
Examples are D–D–π–A-type organic dyes containing (3,6-di-tert-butylcarbazol-N-yl)-N-dodecylcarbazol-6-yl or (3,6-di-tert-butylcarbazol-9-yl)phenyl)-N-dodecylaniline systems as an electron donor moiety (D–D) give the DSSC efficiency reaching >98% of that of the reference N3-based cell.
Fig. DSSC panels
Molecular donor materials employing a novel molecular architecture with three diketopyrrolopyrrole (DPP) chromophores (tri-DPP) in the conjugated backbone are developed for use in solution-processed BHJ solar cells. Solar cell devices fabricated with PC71BM produce a PCE of 5.5%.