A Highly Crystalline and Wide-Bandgap Polydiarylfluorene with β-Phase Conformation toward Stable Electroluminescence and Dual Amplified Spontaneous Emission

Abstract

Bulky conjugated polymers with high crystallinity is the prerequisite for the overall improvement of performance in wide-bandgap semiconductors, including charge transport, photoluminescence quantum yield, processing reliability, and stability. Herein, we report a stable β-phase film of bulky polydiarylfluorene (PODPF) preparing by thermal annealing at ∼220 °C. The β-phase conformation and regular molecular packing are confirmed by UV-vis, photoluminescence (PL), Raman spectra, and grazing incidence X-ray diffraction (GIXD), respectively. Polymer light-emitting diodes (PLEDs) with crystalline and β-phase film serving as the active layer exhibit higher current efficiency of 1.8 cd/A (6.0 V) and more stable electroluminescence over the amorphous one. Surprisingly, mixed conformations in PODPF film produce dually tunable amplified spontaneous emission (ASE) at 463 and 482 nm. Polydiarylfluorenes with quasi-planar conformation will be a promising candidate for the next-generation gain medium toward a broadly tunable lasing and dual-wavelength laser.

Ultrastable Supramolecular Self‐Encapsulated Wide‐Bandgap Conjugated Polymers for Large‐Area and Flexible Electroluminescent Devices

“…For all the effort put into the design of polyfluorenes over the last few decades, the utilization of the fluorene 4,5 position has been completely ignored. Recently, the second planar (β) conformational stable polydiarylfluorenes was designed with a balance between the steric interaction of bulky diphenyl (9‐position) and the entangled attraction of octyl side chain at 4‐position (van der Waals force, vDW) . Herein, we demonstrate a supramolecular approach in plastic electronic (also called supramolecular plastic electronic, SPE) to subtly avoid various pathways for defect generation based on ketone and aggregate formation to construct supramolecular self‐encapsulated polyfluorenes.…”

Dual Amplified Spontaneous Emission and Lasing from Nanographene Films

“…Further, fewer cases of dual ASE have been reported to occur in solid films, and most of them correspond to PFO derivatives. In them, the dual ASE is attributed to the coexistence of two phases of the polymer, which can emit simultaneously [33,34], and/or to the coexistence of a monomer and excimer [35]. Aside from these, dual ASE was found in a bifluorene derivative single crystal, which was related to the emission from two different vibronic replicas [36].…”

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

“…[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°. 30,45 While for β-phase the alternation of side chains leads to formation of a 21 helix, the direction of side chain extension does not necessarily alternate for the glassy-phase.…”