Far-field and hole injection enhancement by noble metal nanoparticles in organic light emitting devices

• Hole injection enhancement have been achieved in OLED with sparse amount of gold and silver nanoparticles.
• The emission intensity has been increased by two times with notable reduction in turn on voltage of OLEDs.
• The reduction in hole injection barrier has been quantified theoretically and it is exposed in XPS and hole only device studies.
• The far-field plasmons of metal nanoparticles also contributed to intensity enhancement in OLEDs which divulge through time resolved photoluminescence technique.

We report the combined effect of plasmonic far-field and improved hole injection towards enhancing the performance of OLEDs by the incorporation of gold and silver (Au and Ag) nanoparticles at the interface of anode/hole transport layer (HTL). The metal nanoparticles incorporated devices facilitate improved hole injection into HTL owing to the shift in vacuum level of anode resulting in three fold enhancement of current density in OLEDs. Hole only devices made with Au and Ag nanoparticles at anodes offer meliorated hole injection than the reference anode due to the reduced injection barrier. X-ray photoelectron spectroscopy analysis further corroborates the alteration of work function of metal nanoparticles infused ITO by exhibiting an abrupt shift in In 3d and Sn 3d photoelectron energy levels. In addition, time resolved photoluminescence spectra reveal that the interaction of far-field plasmons with the device emission accelerates the luminescence of OLEDs further.

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