Luminescence And Electrical Properties Of Poly-p-phenylenebenzobisoxazole

As we know that, lots of problems are in desire need to be solved in electroluminesce devices, such as the conductivity and electroluminescence machnism. One of the approaches is using good materials. For this reason, Poly-p-phenylenebenzobisoxazole is chosed as electroluminescent material for its special largeπconjugated structure and particular properties: n-type polymer and lyotropic liquid crystal.In this paper studies are focus on PBO's optoelectronic properties. And some attempts have done to find out in which concentrations PBO dilute solution would be liquid crystal and the appropriate methods to orient PBO solid fillm.The result of systemic studies on PBO dilute solution and PBO solid film substantiated that there is no aggregation occurs in the solution which was misconceived in some papers. And the fluorenscence quantum efficiency of PBO in MSA dilute solution was estimated in the range of 50% via the method of relative.The electric properties of single-layer device prepared by spin-coating were characterized by direct current-voltage and AC impedance measurements. I-V characteristic was analysized. The current injection mechanism accords with SCLC at lower voltage and trapped along with the voltage increases, when the voltage is higher than 8V, it abbeys the rule of SCLC again. It was found the decomlexation affected by the time of immersion for PBO solid film in deionized water. Longer the time is, lower the conductivity of the device would be. At the same time, AC conductivity changes with frequency. In the LF region, it reflects DC properties of materials. While in the HF region, the dependence of AC conductivities to the frequency isσ=1/R+Aω~n, the index n is about 0.95～0.99. Double-layer electroluminescent devices also have been made and compared with single-layer devices with the relationship between current density or Power density with applied voltage and electroluminescent spectra.It is demonstrated that PBO was liquid crystal at a certain concentration. Our results showed, once PBO in MSA solution at the concentration about 2.9wt%～10wt% and PBO in lewis acid solution at the concentration about 2.5wt%~6wt%, the liquid crystal phase appears. And anisotropic film has been obtained adopting mechanical shearing method.