Improved properties of high molar mass poly(9-vinylcarbazole) and performance as a light emitter compared with the commercial PVK

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Solid-state materials for advanced technology, 2022-12, Vol.286, p.116020, Article 116020
• Main Authors: Barbosa de Brito, Elisa, de Morais, Andreia, Nei de Freitas, Jilian, Valaski, Rogerio, de Fátima Vieira Marques, Maria
• Format: Article
• Language: English
• Subjects: Cationic polymerization; Current efficiency; Emitters; Glass transition temperature; Photoluminescence; Polymerization; Polymers; Polyvinyl carbazole; Substrates; Syndiotacticity
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2022.116020

[Display omitted] •Poly(9-vinylcarbazole) synthesized by cationic polymerization with high yields.•Bimodal PVK with high molar mass, degradation, and glass transition temperatures.•PVK with a bandgap of around 3.49 eV, lower than those reported in the literature.•Evaluation as emitting material in OLEDs assembled using PVK as a single electroluminescent layer.•Photoluminescence spectrum has only a broad emission peak near the visible region, with a lower turn-on voltage and higher luminance and current efficiency. Poly(9-vinylcarbazole), PVK, has been the object of study due to its versatility in polymerization methods. It presents high thermal and photochemical stability and high charge mobility. In the present work, different bimodal high molar mass PVKs were synthesized by cationic polymerization with high yields, above 80 %, and the polymer properties were investigated. The obtained PVKs presented degradation temperatures above 460 °C. The syndiotacticity was around 60 %, and the polymers were amorphous. The glass transition temperature achieved 238 °C. The samples revealed a bandgap value of around 3.49 eV, lower than that reported in the literature. The AFM analysis shows that all the PVK films are smooth, with good substrate coverage and low roughness values. The polymers were evaluated as emitting materials in OLEDs assembled using PVK as a single electroluminescent layer, and the performance was compared to an OLED containing a commercially available PVK. The photoluminescence spectrum presented only a broad emission peak near the visible region at 360-a480 nm. The turn-on voltage (Von) of all synthesized polymers was lower, while luminance (Lmax) and current efficiency values (ηcurr) were higher than those obtained using the commercial PVK.