SOLID-STATE DIODE-LIKE CHEMILUMINESCENCE BASED ON SERIAL, IMMOBILIZEDCONCENTRATION GRADIENTS IN MIXED-VALENT POLY[RU(VBPY)(3)](PF6)(2) FILMS

The electronic conductivity and electrogenerated chemiluminescence (EC L) of thin, electropolymerized films of the fixed-site redox polymer p oly[Ru(vbpy)(3)](PF6)(2) (vbpy = 4-vinyl-4'-methyl-2,2'-bipyridine) on Pt interdigitated array electrodes were examined for both solvent-swo llen and dry films. In both cases emission arose from Ru2+ produced v ia the electron-transfer reaction between Ru3+ and Ru1+ states within the film (Ru = Ru(vbpy)(3)). Dry films contained fixed concentration g radients of Ru3+, Ru2+, and Ru1+ states which were first introduced in an acetonitrile-swollen film via the constant potential oxidation and reduction of Ru2+ at opposing IDA fingers. The gradients were then im mbolized by drying and cooling the film while retaining the inter-elec trode bias (2.6 V). The resulting dried and cooled films responded rap idly to changes in voltage bias and exhibited diode-like characteristi cs, conducting and emitting light at biases greater than or equal to 2 .6 V and undergoing a reverse bias breakdown current, unassociated wit h light emission, at ca. -5.5 V. At 0 degrees C the optimum quantum ef ficiency of solid-state ECL emission (phi(ECL)) was similar to that in solvent-swollen films: 0.0003 photon/electron. In contrast to the dry films, solvent-swollen films were slow to respond to changes in volta ge bias and did not exhibit diode-like behavior.