Organic Microcavity Luminescence Characteristics

Due to the intrinsic broad spectra of the organic materials the chroma of the organic light emitting diode (OLED) can not meet the need of the full color display. It is of great value in the field of the display by introducing microcavity to the OLED because the microcavity can improve the chroma of the device. In this paper, we first discussed the issues, which must be solved in the process of the designing device structure, then we designed and developed the pure red, green, blue and white color emitting microcavity devices. First, we calculated the optical characteristics of the distributed bragg reflector (DBR) and metal mirror and the electric field distri-bution of the different cavity structures. We first deducted the correct expression between the penetration depth and the phase shift of the metal films. Then, we designed a full metal symmetricalλ/2 cavity. By changing the thickness of the metal film we got a serials of the penetration depths of the metal at the different thickness. The experimental results tallied with the simulated ones very well. So we can design the cavity structures accurately under this guidance. By introducing the filler layers, the adjustment of the position of the thin emitting layer was achieved. We studied the effect of the coupling strength between the emission dipole and the electric field of the cavity on the emission intensity for the first time, and found that when the emitter located at the antinode of the electric field of the cavity the PL intensity reached its maximum, while at the node of the electric field the PL intensity reached its minimum. This result is instructive to designing high efficiency microcavity devices. Using the typical MOLED structure of Glass/DBR/ITO/HTL/EML/MgAg, we designed and developed pure red, green, blue and white devices. All of the devices showed better performances in luminescence, chroma and current efficiency than those of the device without cavity. Using the structure of Glass /DBR /ITO /HTL/HTL:ETL/Al a serial cavity devices were made. By changing the weight ratio of HTL and ETL the position of the recombination zone can be controlled. When the ratio is 1:28 the chromatic coordinates of the device are X=0.3054,Y=0.3389, which is close to white light emission. Using two DBR as the reflectors and the PFO film as the active layer, the high Q optical microcavity structure was fabricated. The optical pumped laser characteristics of the polymer were studied in the high Q cavity structure. When pumped by the treble Nd3+:YAG pulsed laser we found laser emission at 460nm.The FWHM is 2.4nm and the threshold power density is 9.7kW/cm2/pulse.