Collision Between Polaron And Exciton In Conjugated Polymers Under The Interchain Coupling

Conjugated polymers are a new kind of functional materials newly developing in recent years. They have characteristic as follows:the shape is easy machining; the price is low; the flexility is good and so on. Meanwhile, their electronic properties show the aspect of both metals and semiconductors. Conjugated polymers have a good prospect for the application. For instance, the oganic light-emitting diodes(OLEDs) and some field effect transistors made by organic metarials have very good luminescent efficiency. All these examples make organic materials to be the hotspot in recent years.Compared with the conventional inorganic materials, conjugated polymers have strong electron-lattice interactions, which result in the close relation between the bond structure and the electronic occupation. When the polymer system are doped with electron or excited by the illumination, the lattic will have a distortion. Conversely, the lattice distortion will astrict the electronic state. Therefore, the elementary carries in conjugated polymers are chared excitations, like soliton, anti-soliton, plus-minus polaron, and plus-minus bipolaron instead of electrons and holes in conventional inorganic materials. In addition, there are some other excitations such as excitons and biexcitons, which composing quasiparticle system of the conjucated polymers. People have done a lot studies on the excitations and acquire fruitful results. These excitations have abundant physical process, such as shaping, exciting, collision, relaxation and so on. In recent years, along with the utilize of solar energy, exploitation of optoelectronic devices and development of liquid-crystal display technic, people have found that the electronic transition of the charged carries such as polarons are tightly related to the process of photoelectric conversion, and the collision between polarons and the other excitations are one of the major cause of the electric transition at the same time. How to see clearly the process of the collision and control the yield of the production have great meaning to improve the photoelectric conversings efficiency of the optoelectronic devices.The results show that interchain coupling have main effect on the yield of the excited polarons, and at the same time the electric field plays a part of regulation. When the interchain coupling is very small, the polaron and the exciton have little interrelationship because they are distrbuted on different chains. As the interchain coupling t(?) increases, the localized degree on the initial chain of both the polaron and the exciton decreases. Meanwhile, the localized degree on another chain increases. When the interchain coupling keeps increasing, the localized degree on the two chains of the polaron and the exciton become the same in order, that is, they extend on the two chains averagely. The two critical point are0.10eV and0.24eV, separately. When0<t(?)<0.10eV, the polaron extends on the two chains from the initial localized state, while the exciton keep the localized state on the initial chain all the time. After the collision, the polaron and the exciton both keep the initial state basically, and the yield of the product is low.When0.10eV<t(?)<0.24eV, the polaron is in averagely extended state while the exciton becomes extending on the other chain. The collision is violent now and the yield of the excited polarons has a qualitative improvement along with the extending of the exciton. When t(?)>0.24eV, the polaron and the exciton are both averagely extended state and the collision is quite violent. The yield of the excitation of the polarons basically stabilizes at the maximum value of25%.