Solution-processed small molecules as mixed host for highly efficient blue and white phosphorescent organic...

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Phosphorescent organic light-emitting diodes (OLEDs) are crucial for advanced display and lighting technologies.
• Solution-processing offers a low-cost fabrication route for OLEDs, but performance is often limited by host material properties.
• 4,4',4″-tris(N-carbazolyl)-triphenylamine (TCTA) is a widely used hole-transporting host material.

Purpose of the Study:

• To investigate the effect of mixed-host systems on the performance of solution-processed phosphorescent OLEDs.
• To enhance charge injection and transport properties by blending TCTA with other small-molecule materials.
• To achieve high efficiency and low driving voltage in blue and white phosphorescent OLEDs.

Main Methods:

• Fabrication of phosphorescent OLEDs using a low-cost solution-process.
• Systematic investigation of mixed-host compositions, specifically TCTA blended with hole-transporting or electron-transporting small molecules.
• Characterization of device performance, including driving voltage, current efficiency, and power efficiency.

Main Results:

• The performance of solution-processed OLEDs is highly sensitive to the mixed-host composition.
• Incorporating 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) into TCTA significantly reduced driving voltage and enhanced efficiency.
• Optimized TCTA:TAPC mixed-host blue OLEDs achieved a maximum current efficiency of 32.0 cd/A and power efficiency of 25.9 lm/W.
• White OLEDs based on TCTA:TAPC demonstrated maximum efficiencies of 37.1 cd/A and 32.1 lm/W, with a low driving voltage of 4.6 V at 1000 cd/m(2).

Conclusions:

• Mixed-host systems, particularly TCTA:TAPC, are effective for improving the performance of solution-processed phosphorescent OLEDs.
• The TCTA:TAPC mixed-host enables the fabrication of high-efficiency, low-voltage blue and white phosphorescent OLEDs.
• Solution-processed OLEDs using the TCTA:TAPC host show performance comparable to state-of-the-art vacuum-evaporated devices.