SELF-ASSEMBLED MULTILAYERS OF CdSe NANOCRYSTALS AND p, n-TYPE MOLECULES FOR PHOTOVOLTAIC. OPTICAL, ELECTROCHEMICAL AND PHTOCONDUCTIVE PROPERTIES

The integration of inorganic semiconductor nanoparticles and organic conjugated polymers leads to composite materials with interesting physical properties1. Their characteristics are promising for applications in light-emitting diodes, photovoltaics, photorefractions, lasers, and biosensors2. In this work, we consider p-type and n-type conduction (Schemes 1 and 2, respectively). The layer-by-layer (LBL) method is used to obtain hybrid organic molecule/inorganic semiconductor nanoparticles multilayer thin films. We choose oligothiophenes (as anionic bipolar amphiphiles) or polythiophenes (bearing anionic substituents aside the polyconjugated chain) for p-type conduction, while a series of linear phenylene-based molecules, bearing carboxylic acid or carboxylate functionalities at both ends are selected for n-type conduction. The inorganic semiconductor component is hexadecylamine-capped CdSe nanocrystals of about 7.5 nm of diameter. The multilayer buildup was monitored by UV-vis spectroscopy and the new hybrid materials were characterized by cyclic voltammetry (CV), UV-vis and FTIR spectroscopy, photoelectrochemistry and photoconductivity .