Tailoring electroluminescence characteristics with enhanced electron injection efficiency in organic light emitting diodes by doping engineering

In present work, by employing doping engineering, we demonstrate a new type of organic light-emitting diodes (OLEDs) constructed by novel hybrid electron-injecting and electron-transporting layers (EITL) with cadmium sulfide (CdS) and Alq₃ as buffer active materials. Our developed OLEDs exhibit highly effective electron injection from cathode to organic layers. Simultaneously, the driving voltage is significantly reduced with Alq₃/Alq₃ doped CdS hybrid EITL structure. Importantly, equipped with 60 nm constant thickness of hybrid layer, the device with 15 nm-thickness of Alq₃ doped CdS exhibit improved performance than the others with the maximum luminance and the maximum of current efficiency 32340 cd/m² at 12 V and 5.92 cd/A at 11.5 V, respectively, with the CIE coordinates almost nearby (0.33, 0.56). And at the current density of 200 cd/m², the current efficiency of the device with EITL was 5.18 cd/A, improved 31% than that of the device non-doped CdS. Such enhanced improvements are attributed to the injection of photo-generated electrons produced by CdS which absorbed the light waves. Our systematic studies and complementary engineering investigations upon highly efficient hybrid OLEDs open new opportunities for innovative applications with optimized integration among performance, dimension and cost in a variety of solid-state lighting field applications, e.g., digital displays, portable systems, smart wearable devices and human–machine interfaces.