(5db) Electronic Device Fabrication from Engineered Inorganic Nanomaterial-Conducting Polymer Composites

Strategies for engineering the integration of inorganic nanomaterials on conducting polymer films for the fabrication of stable, cheap and robust (i) chemical sensors and (ii) Light Emitting Diodes (LEDs) are presented. These strategies involve the use of oxidative Chemical Vapor Deposited (oCVD) conducting polymer films for integrating either inorganic quantum dots or metal nanoparticles for device fabrication. These strategies do not disturb the active quantum dot or metal nanoparticle area and thus require no post-processing for obtaining functional devices.

In the first strategy, the ?COOH functional groups on top of the oCVD conducting polymer films of poly(3,4-ethylenedioxythiophene-co-thiophene-3-acetic acid), P(EDOT-co-TAA), were used for tethering metal nanoparticles. Good electronic interaction between the inorganic and organic layers was ensured by using conjugated linker materials, such as 4-aminothiophenol. For the fabrication of a volatile organic compound (VOC) sensor, the property of a metal of exhibiting a change in work function on exposure to gases was exploited. These work function changes could be translated into conductivity changes upon integration of metal nanoparticles on top of the functionalized conducting polymer films. Selectivity in sensing chemicals was achieved by varying the material of the metal integrated on top of these conducting polymer films. Nanoparticles of palladium and toluene integrated on top of P(EDOT-co-TAA) were observed to selectively detect acetone and toluene, respectively. Concentrations of acetone and toluene as low as 171 ppm and 51 ppm, respectively, were detected using this technique.

In the second case, cadmium selenide/Zinc sulfide (CdSe/ZnS) quantum dots were assembled on top of the oCVD PEDOT films for the fabrication of red LEDs. Electrostatic self-assembly, using poly(diallyl dimethyl ammonium chloride) (PDDA), was employed for obtaining a uniform layer of quantum dots on top of the conducting polymer film. A sputtered thin film of gold served as cathode. The fabrication process was entirely performed under ambient conditions and resulted in an LED stack composed of ITO/PEDOT/CdSe/ZnS/Au. These red LEDs had a threshold voltage of 3.5 V, and exhibited a luminance of 136.6 Cd/m² at an applied voltage of 6 V.