Optimization of Electron Transport Layer Inkjet Printing Towards Fully Solution-Processable OLEDs.

Area of Science:

• Organic electronics
• Materials science
• Device fabrication

Background:

• Inkjet printing offers a cost-effective method for fabricating organic optoelectronic devices.
• Organic light-emitting diodes (OLEDs) are crucial for displays and lighting, but fully printed architectures face challenges.
• Depositing subsequent layers without damaging underlying ones is a key hurdle in printable OLED fabrication.

Purpose of the Study:

• To optimize an ink formulation for printing the electron transport layer (ETL) in bottom-emitting OLEDs.
• To demonstrate the successful integration of a printed ETL into a functional OLED device.
• To advance the development of fully printed OLED architectures.

Main Methods:

• Formulation of a 2,2',2″-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi)-based ink for ETL deposition.
• Identification of an optimal solvent ratio (methanol to diethyl ether) for high-quality ETL printing.
• Integration of the printed ETL into an OLED device with a 5,10-Bis(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)-2,6-dimethylphenyl)-5,10-dihydroboranthrene (tBuCzDBA) emitting layer.

Main Results:

• A specific methanol to diethyl ether ratio was found to enable ETL printing without damaging the underlying emitting layer.
• The optimized printed ETL was successfully incorporated into a complete OLED device.
• The resulting OLED achieved a maximum current efficiency of 6.8 cd/A and a peak luminance of approximately 8700 cd/m².

Conclusions:

• The study presents a viable method for printing the critical ETL in OLEDs using inkjet technology.
• This work signifies a substantial advancement towards achieving fully printed OLEDs.
• The optimized ink formulation and printing process contribute to the goal of low-cost, high-performance organic optoelectronics.