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 primar y photoexcitations in the pyridine-based polymers are singlet excitons . We observe direct intersystem crossing (ISC) on picosecond time scal es with the volume density of triplet excitons varying with the sample morphology (film or powder). These effects are demonstrated clearly b y 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, b oth ''conventional'' diode device and symmetrically configured ac ligh t-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 p olymer-polymer interfaces.