An Easy Approach to Control β-Phase Formation in PFO Films for Optimized Emission Properties

Abstract

We demonstrate a novel approach to control β-phase content generated in poly(9,9-dioctylfluorene) (PFO) films. A very small amount of paraffin oil was used as the additive to the PFO solution in toluene. The β-phase fraction in the spin-coated PFO films can be modified from 0% to 20% simply by changing the volume percentage of paraffin oil in the mixed solution. Organic light emitting diodes (OLEDs) and amplified spontaneous emission (ASE) study confirmed low β-phase fraction promise better OLEDs device, while high β-phase fraction benefits ASE performance.

Gain Properties and Distributed Feedback Laser Performance of 7F6/Poly(Styrene) Blend Films: Potential Core Material for Plastic Optical Fiber Expanding the Bandwidth to Visible Region

“…The ASE threshold can be defined as the pump energy when the FWHM value of the emission spectra decreases to half, compared with the FWHM of PL spectra. In this case, the threshold of the pristine 7F6 film is 0.6 kW cm −2 , which is in the lowest range compared with previous reported ASE thresholds of blue emission polymers and oligomers . This low ASE threshold is a desirable feature which offers more feasibility for blending the oligomer with PS matrix to achieve low threshold and high optical gain.…”

The Importance of Microstructure in Determining Polaron Generation Yield in Poly(9,9-dioctylfluorene)

“…PFO is chosen because chain segments can adopt a well-defined, highly-ordered 'β-phase' conformation whose formation can be carefully and reproducibly controlled by a variety of thin film processing methods. [28][29][30][31][32][33][34] In recent years, a growing number of PFO derivatives and related polyfluorenes have also shown a similar β-phase conformation. [35][36][37][38][39][40][41][42][43][44] Polymer chain segments adopting a β-phase conformation exhibit a planarised interunit torsion angle of ≈ 180°, in comparison to the majority in-plane isotropic 'glassy-phase' segments which adopt a much wider range of more twisted torsion angles of ≈ 120-140°.…”

Direct synthesis of light-emitting triblock copolymers from RAFT polymerization

“…PFO, arguably the best-known blue emitting conjugated polymer, combines thermal and chemical stability with high fluorescence quantum yields and solubility in a range of apolar solvents. 7,15,62 Besides an amorphous and (liquid) crystalline phases, 63,64 PFO is known to form a metastable β-phase, comprising planar chain segments in which the monomers adopt an all-gauge conformation. This results in an extended conjugation length, leading to a red-shift in of the absorption and fluorescence spectrum and increased luminescence quantum yield.…”