Diodo organiko argi-igorlea: aurrekariak, bilakaera eta gaur egungo egoera : Light emitting organic diode: antecedents, evolution and state of the art

Abstract

Light emitting diodes (LEDs) were firstly reported forty years ago. Soon they gained attention due to their suitability for industry. They are actively applied in our daily life as well as in many technological fields as displays or overall in lighting. Compared to common lamps, these diodes consume less energy, and they are more efficient and long lasting. These signatures contribute to a sustainable technological development and to reduce the emission of greenhouse gases due to energy saving. As a matter of fact, the street lighting is being replaced by LED-based lamps and many of the displays are LEDs. Among them, organic LEDs (OLEDs) are successful owing to their low cost and tuneable properties tailoring the molecular structure. These light sources are based on the phenomenon of electroluminescence. To this aim, electrons and holes are driven to the active layer through different pathways. Once there, the electron-hole combination leads to coloured light emission. Herein, the OLED development from its beginning to present is briefly overviewed. We focus on the emission mechanism from the electroactive material (fluorescence, phosphorescence, delayed fluorescence and hyperfluorescence) and on the strengths and weaknesses of each OLED generation. Finally, the future strategies to solve the remaining challenges in OLEDs are addressed.