Simulation for Double Ultrathin Separately Doped Red Organic Light-Emitting Diode

In this study, we employed an ultrathin separately doped organic light-emitting diode (OLED) structure to achieve the lowest turn-on voltage, highest luminance efficiency, and highest electroluminescence. In the simulation part, the spectrum intensity of the main emitting layer (EML) tris(8-hydroxy-quinoline) aluminum (Alq3) photoluminescence (PL) and the full width at half maximum (FWHM) of its Gaussian distribution were modulated to obtain the luminescence spectrum of an ultrathin separately doped device. It is found that as doping concentration increases, the extent of intensity modulation in simulation must be decreased in order to simulate the Alq3 peak drop. This result confirms that when the concentration of a red dopant is high, the red luminance is purer, but the brightness is weaker than that at a lower doping concentration; conversely, at a higher intensity a lower concentration of a red dopant results in more intense luminance, but an orange light, instead of a pure red light is emitted. This study aims to clarify how Alq3 intensity changes in, correspondence to different doping concentrations. For simulation results to coincide with the experimental data, it is deduced that the PL spectrum of 4-(dicuanomethylene)-2methyl-6-(1,1,7,7-tetramethyljulol-idyl-9-enyl)-4H-pyran, DCJT (red dye), exhibits a red shift as doping concentration increases. Finally, we also adjust the thickness of organic layers (hole transport layer/EML) to more accurately approximate simulation results with respect to experimental data. [DOI: 10.1143/JJAP.46.2731]