CuPc:C60 Organic-Fullerene composites together with metals such as Au are found to form efficient hole injection structures for organic light-emitting diodes. C60 concentration of 30 wt.% yielded optimum device characteristics including low driving voltage, high current efficiency, and high thermal stability. In the case of Au/CuPc:C60 anode structure, extremely high current efficiency of ~ 8.7 cd/A and low operating voltage (i.e. 20 mA/cm2 at ~8V) has been achieved in a simple bi-layer device using Alq as emitter. Through a study on single carrier devices, the versatility of the composite injection structure is attributed to that C60 in the composite layer facilitate hole transfer from the metals to the composite whereas CuPc facilitate hole transport and transfer to a hole transport layer.
A novel anode structure comprising a nanocomposite and metal, has enabled highly efficient and stable superluminescent organic light-emitting diodes (SOLED). For C545T singlet green emitter, SOLED can reach 33 cd/A at 1000 cd/m2, doubled the efficiency as comparing to conventional devices with ITO/CuPc structure. More importantly, the SOLED can still hold 24 cd/A at 50000 cd/m2, indicating a highly efficient hole injection capability at ultra-high brightness. In addition, the simulated electronluminescent spectra with angle dependence, agree with experimental results. It is expected that SOLED might find wide applications, not only in display but in general lighting or ultra-high brightness application, by replacing the problematic ITO anode.