Can Be Bent A Study Of The Luminescent Properties Of Organic Electroluminescent Devices

The flexible organic light-emitting devices (FOLED) is an important development direction in the next generation of display technology while it can be fabricated on the flexible substrate for flexible display application. In recently years, more and more works on substrate material, fabrication process, encapsulation technique had been studied. However, the discussion on the optical characteristics of FOLED especially the comparison with that of OLED were less.In this background, the numerical simulations were made mainly surrounding the FOLED's luminescence spectrum and out-coupling efficiency, the optical simulations of FOLED were also analysed in different conditons. the main results in this paper are listed as following:1. Based on the optical microcavity model, the optical characteristics of our FOLED with a structure of top reflecting mirror / organic luminescence layer / bottom reflecting mirror / flexible substrate were discussed. The influence of viewing angle and curvature on the performance of the spectrum was studied, the spectrum of FOLED and that of plane OLED were contrasted as well. It was found that: 1) When substrate was incurvate, the peak value of the spectrum was blueshifted with increased viewing angle, and the extent was broader than that of plane OLED; The peak value of the spectrum was blueshifted with increased curvature; 2) When substrate was excurved, the peak value of the spectrum was redshifted with increased viewing angle, but the extent was slight; the peak value of the spectrum was blueshifted with increased curvature, the extent was approximative with that of plane OLED.2. Based on the geometrical optics model, the expression of FOLED's out-coupling efficiency was studied. The influence of substrate's curvature, substrate's thickness, and organic layer's refractive index on the performance of the FOLED's out-coupling efficiency was studied, and the variation of FOLED and that of plane OLED were contrasted as well. It was found that: 1) When substrate was excurved, the out-coupling efficiency was enhanced with increased substrate's curvature and its thickness, but it was reduced with increased organic layer's refractive index; 2) When substrate was incurvate, the out-coupling efficiency was reduced with increased substrate's curvature and its thickness, it was also reduced with increased organic layer's refractive index. The out-coupling efficiency of OLED was reduced with increased organic layer's refractive index, but it was not involved with the other factors we have discussed.3. A FOLED as a structure of flexible substrate / ITO / organic luminescence layer / Ag was designed, the TracePro simulation of the FOLED's out-coupling in different conditions was studied, and the plots of illuminance and candela distribution were present. It was found that: When substrate was excurved, the luminous flux, illuminance, out-coupling efficiency was larger than those in the condition when substrate was flat. The candela distribution plots were also different in the two conditions. The explanation was present as well.