Synthesis of Polymers with Alternating Organosilanylene and Oligothienylene Units and Their Optical, Conducting, and Hole-Transporting Properties

Abstract

Polymers with alternating mono-, di-, or trisilanylene units and 2,5-oligothienylene groups, [(SiR 2 ) x (C 4 H 2 S) m ] n (R = Me, Et, x = 1−3, m = 2−5), were synthesized and their optical, conducting, and hole-transporting properties were investigated. The UV absorption and emission maxima of the polymers shift to lower energies as the number of thienylene groups ( m ) between the silanylene units increases, while they are little affected by the silicon chain length ( x ). When the polymer films were exposed to FeCl 3 vapor, semiconducting films with the conductivities of 1.3 × 10 - 4 −2.3 × 10 - 1 S/cm were obtained. The conductivities tend to increase with m but decrease with increasing x . The double-layer-type EL devices were fabricated using some of the polymers ( x = 1, m = 3−5; x = 2, m = 4) as the hole-transporting layer and tris(8-quinolinolato)aluminum(III) (Alq) as the electron-transporting-emitter layer. Reducing the number of m and x resulted in a high-voltage shift in the turn-on voltage and a decrease in the maximum current density of the device. The highest luminance of 2000 cd/m 2 was obtained from a device based on the disilanylene−tetrathienylene alternating polymer ( x = 2, m = 4).