Macrornol. zyxwvutsr Symp. 116,27-38 (1997) zyxwv 27 zy PYNDINE-BASED CONJUGATED POLYMERS: PHOTOPHYSICAL PROPERTIES AND LIGHT-EMITTING DEVICES Arthur zyxwvut J. Epstein*, YunZhang Wang, Scott W. Jessen, James W. Blatchford, Darren D. Gebler, Liang-Bih Lin, and Terry. L. Gustafson Dept. of Physics and Dept.of Chemistry, The Ohio State University, Columbus, Ohio 43210-1 106 Timothy M. Swager, and Alan G. MacDiarmid Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, 19104-6323 Abstract: We study the photophysical properties of the pyridine-based polymers: poly@-pyridyl vinylene) (PPyV) and poly@-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. INTRODUCTION Of considerable interest of late in the conjugated polymer field is the electroluminescent capabilities of conjugated polymers such as poly@-phenylene) (PPP) and poly@-phenylene vinylene) (PPV) (Refs. 1,2). The nature of the primary excitations in PPV has been under considerable discussion (Refs. 3-7). Some authors propose that charged carriers, such as polarons or bipolarons, are produced directly upon photoexcitation, due to a strong electron-phonon coupling with a weak Coulombic interaction (Ref. 3). Others suggest that excitons are the primary excitation because of a strong Coulomb interaction (Refs. 4-7). zyx 0 1997 Huthig & Wepf Verlag, Zug CCC 1022-1360/97/$ 04.00