Optimization of OLEDs active layers by wet process

• Autor(a) principal: Teixeira, Francisco Marques
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/38493
• topic: OLEDS; TADF; Solution processed; Opto-electrical properties

In this work, the effects of the solvent used for the active layer materials of an OLED based on TADF emitters were studied. From the different results obtained from the main figures of merit, it was possible to observe that the OLED that used toluene as solvent for the active layer reached a maximum EQE of 14%. With the analysis of the charge transport processes, it was possible to establish an explanatory model for the obtained results. From the color coordinates, it is possible to observe the existance of an emission desviation towards the blue region. This desviation may indicate that a change in the molecular environment as a result of its conformation depending on the different types of solvent used In a complementary way, photophysics studies were also carried out and it was possible to verify that there was no change in the photoluminescence spectrum. Through impedance spectroscopy, an additional characterization of the nature of charge transport processes was carried out. With these results, it was possible to obatin the relaxation times, and correlate them with the electrical properties of the active layer. OLEDs where was used toluene as solvent for the active layer has the lower relaxation time. This may indicate that in this region the interaction between the charges and the defect levels is lower.