Photoluminescent and electroluminescent properties and ultra-fast spectrometric studies of dihydroheptacenes

Photophysical and electrochemical properties of 7,16-dihydroheptacenes (1–3) were investigated in detail. Although their HOMO–LUMO gaps are higher than 3 eV, the organic light-emitting diodes containing 1 as the emitting dopant showed green electroluminescence (λmax ∼ 515 and 550 nm) even at a concentration of the dopant as low as 1%. The green electroluminescence of 1 appears to be originating from an electromeric state (an intermolecular ion pair). The maximum brightness of 190 cd/m2 was observed at a current density of 34 mA/cm2 at operating voltage of 19 V for the device containing 1% 1, and overall performance of the devices decreased with an increase in the doping concentration of 1.