Abstract
Abstract Tandem organic light-emitting device (tandem OLED), in which an interlayer is used to connect several units, shows impressive device performances as compared to that in conventional OLED. In general, an interlayer is composed of two layers: one is low work function metal (ex: lithium) doping electron transport material, which is called n-doped layer; Another is acceptor (ex: 2,3,5,6-Tetrafluoro-7,7,8,8,-tetracyano-quinodimethane, F4-TCNQ) doping hole transport material, which is called p-doped layer. It is generally believed that additional charges (the charges that are not injected from electrode) is generated in the interlayer and sequent injected into the adjacent emitting layer, in which recombination between these charges and injected charges from the electrode takes place and gives rise to light emission. Therefore, the interlayer is also called the “charge generation layer” (CGL). However, the charges in the interlayer is consumed continuously during device operation, it must be a mechanism to regenerate the charges in the interlayer, which is not reported in the literature so far. Therefore, in this thesis, we use time-resolved electroluminescence (TREL) to prove that the charges consumed in the interlayer need to be supplied by the injected charges from the electrode, and the time require for charge supplement is also influence by the number of charges injected from the electrode. The mechanism proposed here can provide insight into the charges generation mechanism in the interlayer of tandem OLED and the highly efficiency LED can be designed accordingly.