Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices

Abstract

In this work, the emission characteristics of a blue fluorophor poly(9, 9-dioctylfluorene) (PFO) combined with a red emitting dye: Bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate)iridium (III) [Ir(MDQ)2(acac)], are examined in two different asymmetric white alternating current field-induced polymer electroluminescent (FIPEL) device structures. The first is a top-contact device in which the triplet transfer is observed resulting in the concentration-dependence of the emission similar to the standard organic light-emitting diode (OLED) structure. The second is a bottom-contact device which, however, exhibits concentration-independence of emission. Specifically, both dye emission and polymer emission are found for the concentrations as high as 10% by weight of the dye in the emitter. We attribute this to the significant different carrier injection characteristics of the two FIPEL devices. Our results suggest a simple and easy way to realize high-quality white emission.

Recent Advances in Alternating Current‐Driven Organic Light‐Emitting Devices

“…The Carroll group also fabricated single‐insulation AC‐driven OLEDs by dispersing MWNTs in the EML for charge injection and transport to achieve effective exciton formation . Furthermore, the usual concentration‐dependence of the emission of the dye was not observed in the hybrid system due to the unique charge carrier‐injection characteristics of AC‐driven OLEDs, which further suggests that tunable color can be achieved in such devices, compared to DC‐driven OLEDs. Accordingly, high‐color‐quality white emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.36, 0.38) and a color rendering index (CRI) of 97.4 was achieved .…”

Non‐Volatile Polymer Electroluminescence Programmable with Ferroelectric Field‐Induced Charge Injection Gate

“…As expected, DC operation of an EL device containing a planar ferroelectric polymer film is not possible due to its insulating properties. The device operation should be, therefore, made by AC with which field induced carriers can be injected from a CIL to an emission layer while direct carrier injection occurs from a top electrode, giving rise to light emission upon exciton recombination . With the unique operation of a device containing a ferroelectric CIG, we are able to develop a novel EL memory whose EL is programmed by DC (voltage pulse) and read by AC at a constant frequency as schematically shown in Figure a.…”

“…Considering the importance of electroluminescence (EL) of organic and polymeric fluorescent materials with its tremendous usages in the variety of applications such as large area and mobile display, solid‐state lighting and sensors operating under either direct current (DC) or alternating current (AC), an electroluminescent organic memory with which EL of the device can be controlled in non‐volatile manner can further broaden the applications of the EL . Since EL of organic emitters is based on excitons of the injected hole–electron carriers, followed by their recombination, it is essential to develop an efficient route not only for programming the carrier injection but also for reliably reading the written EL for a successful EL memory. AC‐driven light‐emitting device can be a novel candidate for an EL memory device application in virtue of the use of dielectric layers as a component, which can be replaced by a ferroelectric one.…”

“…Since EL of organic emitters is based on excitons of the injected hole–electron carriers, followed by their recombination, it is essential to develop an efficient route not only for programming the carrier injection but also for reliably reading the written EL for a successful EL memory. AC‐driven light‐emitting device can be a novel candidate for an EL memory device application in virtue of the use of dielectric layers as a component, which can be replaced by a ferroelectric one.…”

Optimizing the internal electric field distribution of alternating current driven organic light-emitting devices for a reduced operating voltage

“…Several efforts towards AC organic light-emitting devices (AC-OLEDs) have been made in the recent past, and even white-emitting AC-OLEDs have been successfully demonstrated. [4][5][6][7][8] However, the majority of these devices rely on charge injection from one or even both electrodes and show poor performance when operated in a full insulating, capacitively coupled mode, i.e., in a configuration where two insulators prevent charge injection from both electrodes. For this particular configuration, the most promising approach in terms of brightness and efficiency is a p-i-n based architecture in which a single emissive unit is surrounded by doped hole and electron transport layers (HTL/ETL) and by a pair of insulating layers; the whole stack is then sandwiched between two electrodes.…”