LAYER-BY-LAYER ASSEMBLY OF THIN-FILM ZENER DIODES FROM CONDUCTING POLYMERS AND CDSE NANOPARTICLES

Ultrathin films have been prepared by Self-assembling trioctylphosphin e oxide, TOPO, capped n-type 20-40 Angstrom diameter CdSe nanoparticle s and 1,6-hexadecanethiol, HDT, onto p-doped semiconducting polymers, chemically deposited poly(3-methylthiophene), PMeT (for Device A); and electrochemically deposited poly(pyrrole), Ppy (for Device B). The se miconducting polymers have, in turn, been electrochemically layered (f or Device A) or layer-by-layer chemically assembled (for Device B) ont o derivatized conducting substrates. The ultrathin films have been cha racterized by absorption and emission spectroscopy, transmission elect ron microscopy, scanning force microscopy! X-ray-photoelectron spectro scopy,and by electrochemical measurements. By controlling the level of doping into the p-type junction, it was possible to prepare dissymmet rical junctions and observe a rectifying behavior in the forward direc tion and a Zener breakdown in the reverse direction for Au/PMeT/(HDT/C dSe)(3), Device A, and for Au/MEA/Ppy/(HDT/CdSe)(3), Device B. Additio nally, Au/MeA/PAWCdSe (PAH = poly(allylamine hydrochloride)), Au/MEA/P py/PSS/CdSe (PSS = polystyrene sulfonate), and Au/MEA/Ppy/alpha-ZrP/Cd Se (alpha-ZrP = alpha zirconium phosphate) films have been prepared an d characterized.