Polyfluorene polymers blends

A.R. Buckley, M.D. Rahn, J. Hill, J. Cabanillas-Gonzalez, A.M. Fox, and D.D.C. Bradley, Energy transfer dynamics in polyfluorene-based polymer blends, Chem. Phys. Lett., 339 331— 336, 2001. 

The stracture formed by donor acceptor BHJ blends is dependent on the solvent used. Studies of polyfluorene PCBM blends show that choice of solvent controls the segregation of materials within the blend film so that a vertical multilayer structure forms spontaneously in some cases (Bjorstrom and Moons, 2007). Similarly, the choice of solvent in a polymer-polymer blend controls the vertical arrangement of materials and the device performance (Arias et al, 2002). Exploitation of these effects may open new avenues for materials-processing procedures in the organic photovoltaic field. 

J.-S. Kim, P. K. H. Ho, C. E. Murphy, R. H. Friend, Phase Separation in Polyfluorene-Based Conjugated Polymer Blends Lateral and Vertical Analysis of Blend Spin-Cast Thin Films. Macromolecules 2004,37,2861-2871. 

Enhancement of Overall Energy Transfer Efficiency in Polymer Blend Systems and Trapping at On-Chain Heteromolecules (e.g. Fluorenone Molecules in Polyfluorenes)... 

Another fluorene copolymer containing the luminescent dye [4-dicyanomethylene-2-methyl-6-4//-pyran (DCM) as acceptor compound was irradiatiated with UV light in the presence of gaseous triaUcylsilanes. This reagent selectively saturates the C = C bonds in the DCM comonomer units while leaving the fluorene units essentially unaffected. As a result of the photochemical process, the red electroluminescence of the acceptor compound vanishes, and the blue-green electroluminescence from the polyfluorene units is recovered. Compared with previous processes based on polymer blends, this copolymer approach avoids problems associated with phase-separation phenomena in the active layer of OLEDs [256]. 

Kim, J.S., Ho, P.K.H., Murphy, C.E., and Friend, R.H. (2004) Phase separation in polyfluorene-based conjugated polymer blends lateral and vertical analysis of blend spin-cast thin films. Macromolecules. 37, 2861-2871. 

Salim T, Sun S, Wong LH, Xi L, Foo YL, Lam YM. The role of poly(3-hexylthiophene) nanofibers in an all-polymer blend with a polyfluorene copolymer for solar cell applications. J Phy s ChemC 2010 114(20) 9459-9468. 

Anselmo AS, Dzwilewski A, Svensson K, Moons E (2013) Molecular orientation and composition at the surface of spin-coated polyfluorene fuUerene blend films. J Polym Sci, Part B Polym Phys 51(3) 176-182... 

Anselmo AS, Lindgren L, Rysz J, Bemasik A, Budkowski A, Andersson RM, Svensson K, van Stam J, Moons E (2011) Tuning the vertical phase separation in polyfluorene fullerene blend films by polymer functionalization. Chem Mater 23(9) 2295-2302... 

Several organics, e.g. pristine poly(3-octylthiophene), polyfluorene, bifunctional spiro compounds and polyphenyleneethynylene derivative, have been used for fabricating photOFETs. Responsivity as high as 0.5-1 A/W has been achieved in some of these transistors. We have already discussed the bulk heterojunction concept in Chapter 5. The bulk heterojunctions are fabricated using acceptor materials with high electron affinity (such as C<5o or soluble derivatives of C6o) mixed with conjugated polymers as electron donors. PhotOFETs based on conjugated polymer/fullerene blends are expected to show... 

The photophysics of jt-conjugated polymers are reviewed in detail in other chapters of this book. (See, for example, Chapter 3.) Here, we focus on the electronic and photophysical phenomena that occur at the heterojunction between two different semiconductor polymers. The heteroj unctions are formed by combining four different polyfluorene copolymers in blend or bilayer thin films and are investigated using time-resolved and steady-state, temperature- and elec-tric-field-dependent photoluminescence measurements as well as electroluminescence and time-resolved spectroscopy. We review a body of work carried out in our laboratories over the last few years, and published in numerous journal articles (see refs. [13-17]). 

The aim of this chapter is to elucidate the various electronic and optical processes that occur at heterojunctions between two semiconductor polymers. Most of the results presented are related to the presence of localized electronic states at heterojunctions between different polyfluorenes. These have an analog in solution systems of small molecules where they are called exciplex states. Here, we give an overview of the theories that have been developed for small-molecule solution systems (for more details see also [24] and [25]). In Section 2.1.3, we then discuss if and how these are applicable to solid-state films of blended conjugated polymers. 

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