13-09-2014, 11:33 AM
POLYMER LED
POLYMER LED.docx (Size: 40.97 KB / Downloads: 26)
ABSTRACT
Polymer light emitting diode, P-LED, has successfully been fabricated using highly luminous poly derivatives. The P-LED showed a maximum luminance of 55,000cd/m2 This high performance of the device was achieved by employing copolymers of arylene vinylene units as a light-emitting material and a multi-layer structure for the device. Structural and energetical irregularity introduced into the conjugated polymers gave us a highly luminous polymer due to confinement of excitons. The irregularity can be formed by copolymerization of conjugated/non-conjugated segments, m/p-phenylene vinylenes and alkyllalkoxy-substituted phenylene vinylenes. Among the copolymers, the m/p-phenylene vinylene copolymer gave a highly efficient P-LED device due to the balance of the exciton confinement and the charge transporting property .
INTRODUCTION
Organic and polymer light emitting diodes, O-LED and P-LED, have attracted much attention as an accessible flat panel display and have shown good progress in the last few years. Since bright and low-voltage driven O-LED devices were reported by Tang et al.[I], many light-emitting and charge transporting materials and their devices have been reported[2]. Some of the devices showed high luminance and long life time[3]. Catching up with O-LED, a P-LED device was redeveloped in 1990[4] and then many kinds of conjugated polymers known as a conducting polymer were studied as a light-emitting material. P-LED devices using PPV derivatives[5,6], poly [7] and have been reported since 1990.
We have already reported soluble light-emitting poly(2,5-dialkoxy-p-phenylene vinylene), RO-PPV, and its side chain length dependence of fluorescent intensity[9]. Intensity of photo-luminescence, PL, of the RO-PPV film increased with the alkoxy chain length, which is attributable to the decrease of intermolecular interaction and confinement of excitons in the film.