## 1 Introduction  
Since the discovery of the green electroluminescence of _tris_(8-hydroxyquinoline)aluminum Alq\({}_{3}\) by [PERSON] and [PERSON] in 1987 [1], a revolution in the field of electroluminescence on basis of organic materials has been initiated. This research field has garnered significant interest and seen a constant growth, offering the opportunity to the organic light-emitting diode (OLED) technology to immensely progress in terms of materials, device architecture and operational lifetime [2; 3; 4]. Typically, an OLED consists in a stack of organic layers sandwiched between two electrodes. For light emission, one of the electrodes is transparent and in most of the case, the transparent electrode is the anode made of a thin layer of conductive oxide, namely an indium tin oxide (ITO). Despite the outstanding improvements achieved in terms of molecular design and photoluminescence quantum yields, electroluminescence (EL) performance for a given emitter is nonetheless dependent of its PL characteristics but also of the device architecture used to fabricate OLEDs. Thus, a performant emitter investigated in a none-adapted structure will furnish only low electron-to-photon efficiencies. Face to this consideration, promising light-emitting materials such as Firpic [5], Ir(pppy)\({}_{3}\)[6], Ir(piq)\({}_{3}\)[7], DCJTB [8], MEH-PPV [9; 10; 11] or DPVBi [12] have been extensively studied in the literature so that some of these materials have been largely popularized by the number of publications devoted to their studies. Among emitters, phthalimide-based materials are an attractive class of materials by their good electron-transport abilities [13; 14] and their remarkable electron-accepting ability [15; 16]. When combined with the oligophenylinevinylene core, materials with a wide bandgap can be designed, the phthalimide part conferring the electron-transport properties lacking to the oligophenylene central core [17]. To date, this family of fluorescent materials has only been scarcely investigated in the literature. In 2006, 5'-((1,1/1/1)-(2,5-bis(octyloxy)-1,4-phenylene)_bis_(ethene-2,1-diyl))_bis_(2-cyclohexylosinodoline-1,3-dione)  
**Fluo-1** was incorporated as the emitter for single-layered devices [ITO/PEDOT:PSS (50 nm)/emitting layer/LiF(1 nm)/Al], furnishing a maximum brightness of 6200 cd/m\({}^{2}\) at 12 V, a turn-on voltage of 6.0 V and a maximum current and power efficiency of 1.78 cd/A and 0.46 lm/W respectively. More recently, in 2009, its analogue 5\({}^{\prime}\)-((1E,1\({}^{\prime}\)E)-(2,5-_bis_(dodecyloxy)-1,4-phenylene)_bis_(ethene-2,1-diyl)_bis_(2-cyclohexyl-isoulodine-1,3-dione) **Fluo-2** differing from **Fluo-1** by the length of the alkyl chains was examined as a dopant for PVK (poly(\(N\)-vinylcarbazole) See Figure 1) [18].  
The resulting solution-processed devices [ITO/PEDOT:PSS/emitting layer/Ca(50 nm)/Al(100 nm)] only furnished low EL characteristics, with a turn-on voltage of 7.2 V, a maximum luminance of 1358 cd/m\({}^{2}\) and a maximum current efficiency of 0.57 cd/A. In this work, we propose to examine anew the EL performance of **Fluo-2**. Precisely, this fluorescent material was studied in the restrictive context of single-layered organic light-emitting diodes and only low EL characteristics were determined in these conditions. In this work, **Fluo-2** is revisited in the context of multilayered vacuum-processed devices with three different device structures aiming at optimizing its EL characteristics. By using an appropriate device stacking, an enhanced brightness as well as a higher electron-to-photon conversion could be obtained.