This study focuses on a liquid type light-emitting device with simple structure, an organic electrochemiluminescence (ECL) device. To realize long luminescence, polymer ECL devices using π-conjugated polymers, poly(2,5-dioctylphenylene-1,4-ethynylene) (PPE) and poly(3-octylthiophene-2,5- diyl) (P3OT), were fabricated. The luminescence properties of each device were investigated. Both polymer ECL devices exhibit luminescence from an excited-state polymer which is formed by redox and annihilation reaction. In particular, a low threshold voltage of about 2.4 V and long luminescence for about 6000 s were obtained from the P3OT ECL device. This is a longer luminescence than from a typical low molecular ECL device using a ruthenium complex. Moreover, the concentration of emitting material and the frequency applied were important parameters in order to obtain the long luminescence. Applying high frequency AC voltage (5.0 V at 1000 Hz) to the emitting solution with moderate P3OT concentration of 3.0 wt% emitted light for a long period. On the other hand, the PPE ECL device suggested the instability of the radical cation and its luminescence conditions were stringent. Its luminescence was short (about 180 s).
ASJC Scopus subject areas
- Materials Chemistry