Solution-Processed Organic Light-Emitting Diodes Using a Lamination Method

This study aimed to improve the luminous characteristics of laminated OLEDs using the electron injection layer as an adhesive layer by introducing several materials to overcome the limitations of previous studies. We improved the adhesiveness and electron injection ability at the same time by mixing polyethylene glycol (PEG) and D-sorbitol with polyethyleneimine (PEI). In addition, we introduced TPBi and PBD, which are electron-transport and hole-blocking (ET/HB) materials, to improve the electron-transport capability of laminated OLEDs. We fabricated a single-carrier device to analyze the balance of movement of holes and electrons, and a single-substrate OLED device to evaluate the luminance performance by comparing ET/HB materials. Finally, the OLED devices laminating the two substrates were manufactured by applying the optimal conditions found in the above experiments. The results showed that there was a serious imbalance between the electron current and the hole current, which was improved by introducing TPBi and PBD as ET/HB materials. In the case of the laminated OLED device, the device applying D-sorbitol to the adhesive layer showed more stable performance than the device using PEG. As a result, the laminated OLED device applying D-sorbitol showed performance similar to that of the single-substrate OLED, and operated stably even at a high voltage.