Dramatic efficiency improvement in single-layer orange phosphorescent organic light-emitting devices with suppressed efficiency roll-off

Abstract

We have successfully demonstrated efficient single-layer organic light-emitting devices (OLEDs) with a current efficiency of 31.38 cd A À1 . The efficiencies still remain as high as 31.36 cd A À1 , 30.76 cd A À1 and 29.98 cd A À1 at the luminance of 1000 cd m À2 , 5000 cd m À2 and 10 000 cd m À2 . The key feature of the device concept is uniformly doping iridium-bis-(4,6-difluorophenyl-pyridinato-N,C2)-picolinate (FIrPic) into a single organic layer to balance the transport of charge carriers. To better understand the mechanism of single-layer OLEDs, the position of the recombination zone and the influence of FIrPic on the transport properties are also studied in detail. Our work clearly reveals that the performance of the single-layer OLEDs can be dramatically improved by intentionally doping with a phosphorescent dye to balance the transport of charge carriers. This novel and versatile device concept provides a promising simple method to achieve high performance single-layer OLEDs.

Annealing Solution-Processed CuSCN Hole Injection Layer for Blue Phosphorescent Organic Light-Emitting Diodes with Extremely Low Efficiency Roll-Off

“…Material designs for low efficiency roll-offs focus on developing high-performance host molecules of PhOLEDs with balanced hole and electron injection and transportation, ranging from bipolar small molecules, cohost systems, thermally activated delayed fluorescence (TADF) molecules, exciplex with TADF properties, etc. To our knowledge, the best results of EQE roll-offs for blue PhOLEDs are currently as low as 0.53% at 1000 cd m –2 and 4.3% at 10 000 cd m –2 …”

“…To our knowledge, the best results of EQE roll-offs for blue PhOLEDs are currently as low as 0.53% at 1000 cd m −215 and 4.3% at 10 000 cd m −2 . 16 Here, we found that the hole-injection layer (HIL) also has a significant influence on the efficiency roll-off of PhOLEDs; by replacing the widely used poly (3,4- showing an EQE roll-off of 2% at 10 000 cd m −2 and 7% at 20 000 cd m −2 after a set of thermal and current annealing treatments. These results illustrate profound implications for the fabrication of stable blue PhOLEDs using inorganic HILs and proper annealing treatment to optimize the organic/inorganic interfaces.…”

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

“…Recently, single-layer OLEDs have aroused extensive interests due to their simplest structures and superior performance [13,14]. A variety of methods have been suggested to simplify the device structure, among which adopting a bipolar organic material is an efficient one [15][16][17][18].…”