Pyridine-based conjugated polymers: Photophysical properties and light-emitting devices

We study the photophysical properties of the pyridine-based polymers: poly(p-pyridyl vinylene) (PPyV) and poly(p-pyridine) (PPy). The primary photoexcitations in the pyridine-based polymers are singlet excitons. We observe direct intersystem crossing (ISC) on picosecond time scales with the volume density of triplet excitons varying with the sample morphology (film or powder). These effects are demonstrated clearly by examining the millisecond photoinduced absorption characteristics of powder and film forms of PPyV. The pyridine-based polymers have been shown to be promising candidates for polymer light-emitting devices, both ''conventional'' diode device and symmetrically configured ac light-emitting (SCALE) device. Here we examine the role of ''insulating'' layers and their interfaces with the emitting layer and electrodes in the SCALE device operation, with emphasis on the central role of the polymer-polymer interfaces.