Thiophene-Carbazole Based Donor-Acceptor Polymers for OLED Application

Today, organic light emitting diodes (OLEDs) have attracted great interest from researchers, scientists and industry candidates due to their unique features such as low cost, flexibility, light weight and low power consumption and have brought innovation to our lives. The use of conjugated polymers as layers in the OLED device architecture has brought great advantages to this technology and has been a big step towards its commercialization. In this study, conjugated polymers containing thiophene derivatives at the main chain and carbazole exhibited with a quinoxaline bridge in the subunit were designed. In the synthesized polymers, as a result of replacing the thiophene moiety in the main chain with the thienothiophene group, it was observed that the band gap narrowed from 2.28 eV to 2.57 eV and the yellow photoluminescence changed to orange due to the shift in the absorption and emission bands. After the synthesized polymer was characterized with various techniques, thin films were prepared using the spin coating method with simple solution processes and Organic Light Emitting Diodes (OLED) device measurements were performed. Synthesized thiophene-carbazole based donor acceptor polymers (called AP1 and AP2) containing a fluorene in the main chain and a carbazole compound with alkyl chains of different lengths in the side group utilized for polymer-based OLEDs devices. The OLED devices emitted yellow-green electroluminescence at approximately 4 V and in the range of 500-700 nm. The AP1 OLED device was observed to reach saturation by emitting 120 cd/m2 light at around 8 V, while this value was recorded as 85 cd/m2 in the OLED device prepared with AP2 polymer.