Study On The Synthesizes And Photoelectric Properties Of Trimer With Spiro-Fluorene

Organic and polymer light-emitting devices (OLEDs and PLEDs), the novel members of FPDs, have attracted great attentions of the science field and industry for their excellent performance. Industrialization of OLEDs and PLEDs drove the research of new and good-performed organic and polymer light-emitting materials. The structure with spiro-fluorene use only carbon atom to connect two fluorenes. Two planes of fluorene are plumb structure duo to spacial function of 9-C. Its derivatives exhibit excellent chemical and physical properties for this special structure. In this paper, we synthesized a series of trimer with spiro-fluorene structure, which has different substitute at 9-C. Through changing the number of spiro-fluorene unit, these oligomers with same conjugated backbone exhibited different morphology, from crystal to amorphous, via semi-crystal. Through DSC analysis, thermal stability of the oligomer gradually enhanced, along with increasing the number of spiro-fluorene unit. However, only oligomer TPHP exhibited stable amorphous morphology. All optical physics properties have only slight difference between these oligomers, indicating that different side chain at 9-C of fluorene had less effect on electronic structures of oligomer backbone. The oligomer TPPP with full spiro-fluoren unit exhibited strong crystalline due to molecular rigidity. We observed change of morphology after annealing at different temperature for 2h under an argon atmosphere by atomic force microscopy (AFM). While temperature enhancing, the surface of the film was quite rough and the spot of the crystal increased. Two kinds of crystal which is grain and dendron appeared simultaneity at 170°C. The shape of crystal lie on orientation crystal center. Through fluorescent microscope it proved that fluorescence of the crystal was enhanced. The electroluminescent devices using oligomers TPPP, TPHP and THPH as emitting layer exhibited blue light emission, their C.I.E (0.16, 0.07) approached standard blue light. We fabricated multilayer devices with the configuration ITO/ PEDOT:PSS/TCTA(40nm)/oligomer(30nm)/BCP(10nm)/Alq3(20nm)/LiF/Al. The devices using TPPP and TPHP as the emitting layer, which exhibit excellent thermal stability, exhibited comparative electroluminescent capability, but the devices using THPH as the emitting layer showed not better capability relative. The EL capability of amorphous oligomer TPHP was not better than the EL capability of crystal oligomer TPPP, because it can not bring the change of morphology at brief time. However, life of the devices using THPH as the emitting layer will better than using TPPP as the emitting layer affirmatively. Previous investigations have demonstrated that the injection of electrons predominates for fluorene based polymers and oligomers. To increase the efficiency of device, hole injection has to be significantly boosted. The introduction of hole-transporting chromophores, c.a. carbazole, into the fluorene-based oligomers may promote the injection and transport of holes through their thin film. Compared with oligomer TPPP, the first oxidation potential of oligomer TCPC was reduced obviously (0.13V). These features...