Systems for displaying images. An exemplary embodiment of a system comprises an organic electroluminescent diode, having a hole injection layer. The hole injection layer comprises compounds having the structure showing in formula wherein at least one of two adjacent R1 groups link together with the carbon atoms to which they are attached to form a saturated ring system having from 4 to 20 atoms, and remaining R1 and R2 are the same or different and comprise hydrogen or halogen atom.