Highly Efficient Energy Transfer in Light Emissive Poly(9,9-dioctylfluorene) and Poly(p-phenylenevinylene) Blend System

Abstract

A polymer blend system F81–x :SY x based on poly­(9,9-dioctylfluorene) (F8) from the family of polyfluorenes (PFO) and a poly­(para-phenylenevinylene) (PPV) derivative superyellow (SY) shows highly efficient energy transfer from F8 host to SY guest molecules. This has been realized due to a strong overlap between F8 photoemission and SY photoabsorption spectra and negligibly low self-absorption. The steady-state and time-correlated spectroscopic measurements show an increased photoluminescence quantum efficiency (PLQE) and lifetime (τ) of SY, with an opposite trend of decreasing PLQE and τ of F8 excitons with increasing SY concentration, suggesting the Förster resonance energy transfer (FRET) to be the main decay pathway in the proposed system. The systematic study of the exciton dynamics shows a complete energy transfer at 10% of SY in the F8 host matrix and a Förster radius of ∼6.3 nm. The polymer blend system exhibits low laser and amplified spontaneous emission thresholds. An ultrahigh efficiency (27 cd·A–1) in F81–x :SY x based light emitting diodes (LED) has been realized due to the intrinsic property of a well-balanced charge transport within the emissive layer. The dual pathway, that is, the efficient energy transfer between the blended molecules via resonance energy transfer, and the charge-traps-assisted balanced transport makes the system promising for achieving highly efficient devices and a potential candidate for lasing applications.

Short contacts between chains enhancing luminescence quantum yields and carrier mobilities in conjugated copolymers

“…The energy gap law predicts fast non-radiative recombination in low E g materials 21 , while the rate of radiative (spontaneous) emission increases with E g 22 . Therefore, low energy gap polymers (with E g < 1.8 eV) typically have low Φ, and the most fluorescent polymers— including poly(9,9-di-n-octylfluorenyl-2,7-diyl) (F8, Φ = 0.65, E g = 3.0 eV 23 ) and poly(9,9-dioctylfluorene- alt -benzothiadiazole) (F8-BT, Φ = 0.5, E g = 2.5 eV 24 )—have E g > 2.0 eV. On the other hand, in Fig.…”

Thermal‐Responsive Phosphorescent Nanoamplifiers Assembled from Two Metallophosphors

“…We notice that the emission amplification by lightharvesting and EnT in assembled systems and conjugated polymers have been reported with emissive acceptors. [21] However,t he emission amplification of an ACQc ompound in crystalline materials is unprecedented. It should also be noted that the highly ordered crystalline structures of the nanotube sample are important for the efficient EnT and emission amplification.…”

Boosting the Stimulated Emission Properties of Host:Guest Polymer Blends by Inserting Chain Twists in the Host Polymer

“…A threshold of 23 µJ cm −2 was for instance obtained upon 387 nm photoexcitation with 120 fs pulses and similar values are reported in other yellow emitting polymer systems. [ 56–59 ] On the contrary, 1Ph:F8BT exhibited uncompleted ASE, whereas 3Ph:F8BT did not show evidence of linewidth narrowing, even upon pumping with the highest fluence. This result is striking in view of the efficient energy transfer and high Φ PL observed in the three blends and suggests the presence of an internal loss mechanism that could counterbalance ASE.…”