Highly Efficient Single-Layer Phosphorescent Organic Light-Emitting Diodes Based on Co-Host Structure.

Tianyu Zhang,Ping Chen,Ren Sheng,Asu Li,Mingyang Sun

doi:10.3390/ma13092029

Tianyu Zhang, Ping Chen + Show 3 more

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https://doi.org/10.3390/ma13092029

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Abstract

High-efficiency single-layer organic light-emitting diodes (OLEDs) based on a simple structure doped with iridium(III) bis(4-phenylthieno[3,2-c]pyridinato-N,C2′) acetylacetonate (PO-01) as emission dyes are realized, achieving maximum current efficiency (CE) and power efficiency (PE) of 37.1 cd A−1 and 33.3 lm W−1 as well as low turn-on voltage of 3.31 V. Such superior performance is mainly attributed to the employment of a uniform co-host structure and assisted charge transport property of phosphors dyes, which were in favor of the balance of charge carrier injection and transport in the single emitting layer (EML). Moreover, systematic researches on the position of exciton recombination region and the dopant effect on charge carriers were subsequently performed to better understand the operational mechanism. It could be experimentally found that the orange emitting dopants promoted the acceleration of the charge carriers transport and raised the exciton recombination efficiency, eventually leading to an excellent performance of single-layer OLEDs.

Highlights

Organic light-emitting diodes (OLEDs) have gained considerable focus on the applications in both lighting technology and organic flat-panel display due to their high efficiencies, self-emission properties, and compatibility with ease of processing and reduced power consumption [1,2,3,4,5].Phosphorescent OLEDs (PhOLEDs) represent an effective way to obtain advanced performance due to their intrinsic property of harvesting both singlet and triplet excitons, attaining maximum internal quantum efficiency of nearly 100% [6,7,8,9,10]
In order to realize excellent performance, one universal strategy is the adoption of the multilayer structures which include carriers transport layers, exciton blocking layers, or extra space-layers to eliminate exciton quenching and balance charge carriers [11]
Fabricating OLEDs with multiple layers will inevitably increase the use of materials and fabrication steps, presenting new obstacles to the commercial application of

Summary

Introduction

Phosphorescent OLEDs (PhOLEDs) represent an effective way to obtain advanced performance due to their intrinsic property of harvesting both singlet and triplet excitons, attaining maximum internal quantum efficiency of nearly 100% [6,7,8,9,10]. In order to realize excellent performance, one universal strategy is the adoption of the multilayer structures which include carriers transport layers, exciton blocking layers, or extra space-layers to eliminate exciton quenching and balance charge carriers [11]. Fabricating OLEDs with multiple layers will inevitably increase the use of materials and fabrication steps, presenting new obstacles to the commercial application of OLEDs. In consequence, how to simplify the device structure and balance the charge carriers seem to be very meaningful and imperative. Note that the single-layer OLED with only one organic layer is considered as a promising approach for its simplified structure [12]

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