Enabling highly-efficient OLED with solution-processed nanocrystalline copper phthalocyanine hole-injection/transport layer

We report solution-processed nanocrystalline copper-phthalocyanine (CuPc) as a hole-injection/transport layer used to maintain efficient hole injection and transport into the emissive layer. The efficacies and efficiencies of the devices with nanocrystalline CuPc hole-transport layer and control device fabricated poly (3,4-ethylene dioxythiophene)-poly(styrene-sulfonate) (PEDOT:PSS) are investigated. As a result, organic light-emitting diode (OLED) employing the CuPc layer exhibits maximum efficiencies such as a power efficiency (PE max ) of 46.7 lmW −1 and an external quantum efficiency (EQE) of 12.1% along with a current efficiency (CE max ) of 44.1 cdA −1 , which are expressively improved as comparing with PEDOT:PSS based control device. We also observed changes in PE max from 32.1 to 39.7 lmW −1 , CE max from 40.3 to 51.7 cdA −1 and EQE max from 13.0 to 16.2% in thermally activated delayed fluorescence emitter based OLEDs as PEDOT:PSS is replaced with CuPC. This enhancement in all OLED device performance may be attributed to the decreased hole injection barrier at the anode and emissive layer interface. Furthermore, CuPC has been incorporated as a p-type channel to fabricate thin-film transistors (TFTs). CuPC possesses good mobility as comparing with PEDOT:PSS. We believe that the CuPc layer is a promising candidate to achieve high-performance next-generation OLEDs for lighting applications and TFTs.