High efficient Light-Emitting Electrochemical Cells based on ionic liquids 1,2,3-triazolium

Abstract

Abstract The Light-Emitting Electrochemical Cell (LEEC) is one of the simplest kind of electroluminescent solid-state devices. Generally, they are fabricated with only one emitting material layer (EML), so-called active emission layer, that consist of an emitter material mixed with an ionic electrolyte. Apart from the electrolyte, their structure is similar to that of a single layer organic light-emitting diode (OLED). Not only LEECs assemble most of OLEDs applications and their technological advantages, but they also bring additional ones such as (i) low dependence of the electrodes work function, (ii) low dependence to the EML thickness, (iii) low operation voltage and high brightness and finally (iv) LEECs can be printed or sprayed in large areas. To investigate the performance of ionic liquid (IL) based devices we synthesized four organic salts that were compared with devices using four inorganic salts commonly used as electrolyte for LEECs. All devices were fabricated with a commercial poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) as emitter polymer. As a result, we showed that the best device performance was achieved with the Ionic Liquid 1-dodecyl-4-(hydroxymethyl)-3-methyl-1H-1,2,3-triazol-3-ium iodide (dohmtI) presenting a current efficiency of 3.6 cd/A, an external quantum efficiency (EQE) of 1.4% as well as a luminance of 3.2 × 104 cd/m2. Despite the use of MEH-PPV, a polymer not so efficient when compared to the state-of-art of the novel polymers employed nowadays, our realization showed these new ILs have been able to provide the specific requirements of the LEEC devices.