Self-Assembling Azaindole Organogel for Organic Light-Emitting Devices (OLEDs)

This study reports on the use of a self-assembling organogel, 5-(4-nonylphenyl)-7-azaindole (1), as a new emitter in small-molecule organic light emitting devices (OLEDs). The theoretical calculations along with the photophysical characterization studies suggest the coexistence of the monomer and dimer species at high concentration of compound 1. The presence of this type of dimer (formed via H-bonding) is responsible for the increased emission. However, the most notable feature is the 3D network of vastly interconnected fibers formed in the organogel that modifies the photophysical properties. Based on this, several OLED architectures are made in order to understand the mechanism involved in the electroluminescence (EL) behavior of 1. Although the position of the EL spectra differs from that of the photoluminescence (PL) spectra, the trends observed in the device properties perfectly match with dimer formation. In this framework a better device performance is associated to a higher efficiency of dimer formation, which optimizes in the OLED prepared from the organogel. Therefore, these results show that the rational combination of a moiety showing a strong PL intensity increased upon aggregation with organogel properties is an efficient strategy to create alternative emitters for OLED devices.This work was financially supported by the MICINN and Ministry of Economy and Competitiveness of Spain through projects (CTQ2013‐40562‐R, CTQ2014‐56422‐P). C. Martín thanks the Research Foundation‐Flanders for her postdoctoral fellowship. G.M. thanks the Ministry of Economy and Competitiveness for a “Ramón y Cajal” contract (RYC‐2013‐12772). The authors are also indebted to Belspo program through IAP VI/27 and VII/05 and to the KULeuven Research Fund through GOA 2011/3 and C14/15/053. The authors gratefully acknowledge financial support from the European Union's Seventh Framework Programme (FP7/2007‐2013 under grant agreement no. 310651 SACS)