Synthesis Of Polyfluorene And PPV Derivatives And Study On Photo-Electroluminescent Properties

Since the initial discovery of polymeric electroluminescence device (PLEDs) reported in 1990, PLEDs have attracted considerable interest because of their potential application in flat panel displays. PLEDs offer advantages of low turn-on and operating voltages, wide viewing angles and light weight. The range of colors available from PLED spans the entire visible spectrum. Polyfluorene and PPV derivatives have high PL and EL efficiency, good thermal properties, ant-oxidation and good solubility in common organic solvents.In this paper, we have synthesized novel Polyfluorene and PPV derivatives, and the thermal properties, optical properties, electrochemical properties and the single-layered devices based on these polymers are evaluated.1. We design and synthesize two polymers (P1 and P2) by Yamamato coupling reaction based on 9,9-di-octyloxylfluorene and 9-(4-tert-butyl-phenylenemethene)- fluorene monomers, and the solubility, thermal and light-emitting properties of synthesized polymers are discussed in detail. The introduction of 4-tert-butyl-phenyl- enemethene (PTBP) side group into polyfluorene backbone improves planar conformation and adjusts the energy levels to be better charge carrier mobility compared to poly (9,9-dialkyl)fluorenes, which the energy levels of P1 and P2 are 2.38 and 2.47 eV, respectively. The single-layered PLED based on P2 with the configuration of ITO/PEDOT/ P2/Ca/Al emits green light. EL device of P2 has maximum brightness of 603 cd/m2 with maximum emitting number at 540 nm.2. A series of polymers (P3, P4 and P5) are synthesized by Heck coupling reaction based on alkylfluorene, biphenylene, p-phenyl units. The copolymers of P3, P4 and P5 show good thermal stability with weight-loss temperatures higher than 380 oC and the glass-transition temperatures are 108, 104 and 70 oC, respectively. The DSC data of polymers indicate that the three polymers are amorphous. Compared P3 with P4, the difference of the visible spectrum is that the electron-donating long side chain makes the backbone of the polymers twisting, and consequently reduces the effective conjugated length resulting in blue-shift of the absorption and emission in dilute solution and film state. The light-emitting color is effectively controlled through biphenyl and PPV unit introduced in the main chain of polyfluorene.3. A series of novel polyfluorene-co-PPV derivatives (P6 and P7) are synthesized based on PTBP side group of the fluorene unit, and PTBP substituent is used to enhance...