Solution-Processed Phosphorescent Organic Light-Emitting Diodes with Ultralow Driving Voltage and Very High Power Efficiency

Abstract

To realize power efficient solution-processed phosphorescent organic light-emitting diodes (s-PhOLEDs), the corresponding high driving voltage issue should be well solved. To solve it, efforts have been devoted to the exploitation of novel host or interfacial materials. However, the issues of charge trapping of phosphor and/or charge injection barrier are still serious, largely restraining the power efficiency (PE) levels. Herein, with the utilization of an exciplex-forming couple 4, 4′, 4″ -tris[3-methylphenyl(phenyl)amino]triphenylamine (m-MTDATA) and 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB), the efficient charge injection and transporting, barrier-free hole-electron recombination for the formation of the interfacial exciplex, and elimination of charge traps of phosphors in the emissive layer are realized simultaneously, resulting in a turn-on voltage of 2.36 V, a record high PE of 97.2 lm W−1, as well as extremely low driving voltage of 2.60 V at 100 cd m−2, 3.03 V at 1000 cd m−2 and 4.08 V at 10000 cd m−2. This report is the first time that the PE performance of s-PhOLED approaches 100 lm W−1 high level, even superior to the corresponding state-of-the-art performance of the same color vacuum-deposited PhOLED (v-PhOLED) counterpart. We anticipate this report opens a new avenue for achieving power efficient monochromatic and white s-PhOLEDs with simple structures.

Smart Design on the Cyclometalated Ligands of Iridium(III) Complexes for Facile Tuning of Phosphorescence Color Spanning from Deep‐Blue to Near‐Infrared

“…This is probably due to the lower PLQY of Ir6 , which results in an inefficient harvesting of the triplet excitons in its device D Ir6 . In addition, the gradual deepening of the LUMO levels of phosphors in Ir4 – Ir6 would increase the energy barrier for electron transportation from the LUMO of mCP to that of the phosphors (Figure S4b, Supporting Information) and lead to nonbalanced carriers in EML of devices D Ir4 –D Ir6 . The increased energy barrier resulted in the increase of turn‐on voltages ( V on ) of devices D Ir2 –D Ir6 to over 5 V (Figure b and Table ).…”

Interface Effect on Efficiency Loss in Organic Light Emitting Diodes with Solution Processed Emitting Layers

“…Even with the same multilayer architecture, most OLEDs with a solution processed EML have lower efficiencies than their thermal‐evaporated counterparts . One fundamental difference between evaporated and solution processed films is the molecular packing.…”

A Novel Blade‐Jet Coating Method for Achieving Ultrathin, Uniform Film toward All‐Solution‐Processed Large‐Area Organic Light‐Emitting Diodes

“…Furthermore, for the large‐sized OLED devices, esthetically disturbing nonuniform light‐emission features are mostly affected by nonuniformly coated multilayered films; this remains as one of the primary obstacles to commercializing solution‐processed OLEDs . Recently, many research groups have developed extremely high‐efficiency soluble OLED materials comparable to LEDs . However, developments in printing technology for OLED applications have not been so actively researched, and these technologies are still in their infancy.…”