Fabrication of organic electrochemiluminescence devices with π-conjugated polymer materials

Abstract

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 pconjugated polymers, poly(2,5-dioctylphenylene-1,4-ethynylene) (PPE) and poly(3-octylthiophene-2,5diyl) (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).

Multi-color microfluidic electrochemiluminescence cells

“…In contrast, the emitting layer of traditional ECL cells consists of well-established OLED materials dissolved in organic solvents such as acetonitrile [8], 1,2-dichlorobenzene [8,11], benzonitrile [9], and N, N-dimethylformamide [12]. Several studies on ECL have reported on the use of fluorescent dyes [8,12,14] and phosphorescent dyes [9].…”

“…In the current technology, liquid OLEDs and ECL cells typically have a simple device structure fabricated by sandwiching a selected liquid emitter between two glass substrates with electrodes. The gap between the electrodes was preserved by approximately a few micrometers to several hundred micrometers using spacer materials such as insulating films [11], wires [12], glass beads [13], and glass rods [14]. The use of liquid emitters as the emitting layer is expected to provide flexible and crack-free light-emitting layers under repeated bending.…”

“…Several fabrication methods for multi-color OLEDs have been proposed, including vacuum deposition of small molecular organic materials through a shadow mask [2] as well as solution processes such as screen [3,4] and ink-jet printing [5] for electroluminescent polymers. On the other hand, light-emitting devices based on liquid-emitting materials have been reported, such as liquid OLEDs [6,7] and electrochemiluminescence (or electrogenerated chemiluminescence) (ECL) cells [8][9][10][11][12][13][14][15]. Similar to OLEDs that employ solid-state emitters, liquid OLEDs and ECL cells can provide self-emission under appropriate applied voltages.…”

Multi-color microfluidic organic light-emitting diodes based on on-demand emitting layers of pyrene-based liquid organic semiconductors with fluorescent guest dopants

“…In order to obtain the patterned multi-color solid-state emitting layers on a single panel, several fabrication methods have been proposed, including the vacuum deposition of small molecular organic materials through a shadow mask [3] and solution processes such as screen [4], gravure [5], and ink-jet printing [6] for electroluminescent polymers. On the other hand, there has been increasing interest in light-emitting devices based on liquid emitters such as liquid OLEDs [7][8][9][10][11] and electrochemiluminescence (or electrogenerated chemiluminescence) (ECL) cells [12][13][14][15][16][17]. ECL phenomena have been studied since the 1960s [18,19], and the emitting layer of traditional ECL cells typically consists of wellestablished OLED materials dissolved in several organic solvents [13].…”

“…In addition, from the viewpoint of the device design, there are technical challenges associated with multi-color light emission features because conventional liquid OLEDs and ECL cells were designed to have a single liquid emitter sandwiched between two electrode-coated glass substrates. The gap distance between the electrodes for the liquid emitting layer was preserved by approximately a few micrometers to several hundred micrometers using spacer materials [7,[13][14][15][16]. Therefore, the development of patterning methods that are employed for small amount of different liquid emitters on a single device is an important step for developing functional multi-color liquid-based light-emitting applications.…”