| Autor: |
Hauyon RA; Research Laboratory for Organic Polymers (RLOP), Faculty of Chemistry and of Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile., Fuentealba D; Laboratorio de Estructuras Biosupramoleculares, Facultad de Química y de Farmacia, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile., Pizarro N; Facultad de Ciencias Exactas, Departamento de Ciencias Químicas, Universidad Andrés Bello, Viña del Mar 2520000, Chile., Ortega-Alfaro MC; Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior, Cd. Universitaria, Coyoacán, Mexico City 04510, Mexico., Ugalde-Saldívar VM; Departamento de Química Inorgánica y Nuclear, Facultad de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Cd. Universitaria, Coyoacán, Mexico City 04510, Mexico., Sobarzo PA; Research Laboratory for Organic Polymers (RLOP), Faculty of Chemistry and of Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile., Medina J; Research Laboratory for Organic Polymers (RLOP), Faculty of Chemistry and of Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile., García L; Research Laboratory for Organic Polymers (RLOP), Faculty of Chemistry and of Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile., Jessop IA; Organic and Polymeric Materials Research Laboratory, Department of Chemistry, Universidad de Tarapacá, Arica 1000007, Chile., González-Henríquez CM; Laboratory of Nanotechnology and Advanced Materials (LNnMA), Chemistry Department, Universidad Tecnológica Metropolitana, Santiago 8940577, Chile.; Programa Institucional de Fomento a la Investigación, Desarrollo e Innovación (PIDi), Universidad Tecnológica Metropolitana, Ignacio Valdivieso 2409, Santiago 8940577, Chile., Tundidor-Camba A; Research Laboratory for Organic Polymers (RLOP), Faculty of Chemistry and of Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile.; UC Energy Research Center, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile., Terraza CA; Research Laboratory for Organic Polymers (RLOP), Faculty of Chemistry and of Pharmacy, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile.; UC Energy Research Center, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile. |
| Abstrakt: |
In the search for solution-processable TADF materials as a light emitting layer for OLED devices, polymers have attracted considerable attention due to their better thermal and morphological properties in the film state with respect to small molecules. In this work, a new polymer ( p -TPS-DMAC-TRZ) with thermally activated delayed fluorescence (TADF) light-emitting characteristics was prepared from a conjugation-break unit (TPS) and a well-known TADF core (DAMC-TRZ). This material was designed to preserve the photophysical properties of DAMC-TRZ, while improving other properties, such as thermal stability, promoted by its polymerization with a TPS core. Along with excellent solubility in common organic solvents such as toluene, chloroform and THF, the polymer (M n = 9500; M w = 15200) showed high thermal stability (TDT 5% = 481 °C), and a T g value of 265 °C, parameters higher than the reference small molecule DMAC-TRZ (TDT 5% = 305 °C; T g = 91 °C). The photoluminescence maximum of the polymer was centered at 508 nm in the solid state, showing a low redshift compared to DMAC-TRZ (500 nm), while also showing a redshift in solution with solvents of increasing polarity. Time-resolved photoluminescence of p -TPS-DMAC-TRZ at 298 K, showed considerable delayed emission in solid state, with two relatively long lifetimes, 0.290 s (0.14) and 2.06 s (0.50), and a short lifetime of 23.6 ns, while at 77 K, the delayed emission was considerably quenched, and two lifetimes in total were observed, 24.6 ns (0.80) and 180 ns (0.20), which was expected from the slower RISC process at lower temperatures, decreasing the efficiency of the delayed emission and demonstrating that p -TPS-DMAC-TRZ has a TADF emission. This is in agreement with room temperature TRPL measurements in solution, where a decrease in both lifetime and delayed contribution to total photoluminescence was observed when oxygen was present. The PLQY of the mCP blend films with 1% p -TPS-DMAC-DMAC-TRZ as a dopant was determined to be equal to 0.62, while in the pure film, it was equal to 0.29, which is lower than that observed for DMAC-TRZ (0.81). Cyclic voltammetry experiments showed similarities between p -TPS-DMAC-TRZ and DAMC-TRZ with HOMO and LUMO energies of -5.14 eV and -2.76 eV, respectively, establishing an electrochemical bandgap value of 2.38 eV. The thin film morphology of p -TPS-DMAC-TRZ and DMAC-TRZ was compared by AFM and FE-SEM, and the results showed that p-TPS-DMAC-TRZ has a smoother surface with fewer defects, such as aggregations. These results show that the design strategy succeeded in improving the thermal and morphological properties in the polymeric material compared to the reference small molecule, while the photophysical properties were mostly maintained, except for the PLQY determined in the pure films. Still, these results show that p-TPS-DMAC-TRZ is a good candidate for use as a light-emitting layer in OLED devices, especially when used as a host-guest mixture in suitable materials such as mCP. |
