Efficient Blue and Yellow Organic Light-Emitting Diodes Enabled by Aggregation-Induced Emission

Venkatramaiah, N and Kumar, G Dinesh and Chandrasekaran, Yogesh and Ganduri, Ramesh and Patil, Satish (2018) Efficient Blue and Yellow Organic Light-Emitting Diodes Enabled by Aggregation-Induced Emission. In: ACS APPLIED MATERIALS & INTERFACES, 10 (4). pp. 3838-3847.

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Abstract

A new class of donor-bridge-acceptor (D-pi-A) pi-conjugated light-emitting molecules comprising carbazole as donor and maleimide (Cbz-MI, Cbz-MI(d)), phthalimide (Cbz-Pth) as acceptor units with phenyl ring as spacer have been synthesized in good yields. These compounds exhibit high quantum yield with three distinct emission colors yellowish-green (Cbz-MI), bright yellow Cbz-MI(d), and sky blue (Cbz-Pth) in the solid state. Single-crystal X-ray and quantum chemical calculations reveals that twisting of the phenyl rings with high torsional angle on maleimide and phthalimide units reduce the effective inter-chromophore electronic coupling, furnish dramatic changes in their photophysical properties in solution and solid states. Intriguingly, Cbz-MI(d) and Cbz-Pth exhibits a unique aggregation-induced blue-shifted emission (AIBSE) due to restricted intramolecular rotation (RIR) process, While Cbz-MI shows red-shifted emission in the solid state. The solvatochromic study reveal that combined RIR and excited state migration augment AIE (aggregation-induced emission) properties. The electrochemical properties reveal that Cbz-MI exhibits high oxidation propensity while Cbz-Pth shows low reduction values. Subsequently, organic light-emitting diodes (OLEDs) were fabricated with a simple three-layer device containing Cbz-Pth and Cbz-MI(d) as emitting layers. Cbz-MI(d) exhibits high performance yellow OLED with an external quantum efficiency exceeding similar to 4.1% and a brightness exceeding similar to 73915 cd/m(2), which is among the best performance reported for bright yellow fluorescence organic light-emitting diodes.

Item Type:	Journal Article
Publication:	ACS APPLIED MATERIALS & INTERFACES
Publisher:	AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Additional Information:	Copy right for the article belong to AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	08 Mar 2018 19:06
Last Modified:	08 Mar 2018 19:06
URI:	http://eprints.iisc.ac.in/id/eprint/59135

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