Blends of Polyfluorenes with Other Polymers

It was shown that adding low oxidation potential material to PFs can stabilize the emission color and increase the device efficiency [321]. However, using low-molecular-weight organic dopants causes several problems such as phase separation and crystallization. These problems can be partially solved by using polymer blends. Cimrova and Vyprachticky [334] reported 

Since the ionization potential of 238 matches closely the work function of PEDOT (5.1-5.3 eV) [335], the hole injection is dramatically improved. Accordingly, the device ITO/PEDOT/237 238(7 3)/Al has a significantly improved EL efficiency, tjel= 1.5cd/A, two orders of magnitude higher than that of single-layer PLED with 237, six times higher than that of bilayer PLED with triarylamine polymer HTL, and almost twice as high as that of PF blends with low molecular triphenylamine HT materials (in device with Ca electrode) [321]. 

Enhanced environmental stability was recently demonstrated for PLED with PFO 196/gold nanoparticle (5-10 nm) nanocomposite-emitting layer [337]. In addition, the gold nanoparticle-doped PLEDs (1.5 x 10-5 volume fraction of Au) demonstrated improved luminescent lifetime and 2-3 times higher QE, compared with pure PFO-based PLED. 

---