UV-converting blue-emitting polyfluorene-based organic-inorganic hybrids for solid state lighting

Abstract

Solid state lighting (SSL) revolutionized the light sources and displays market. Challenges include the seek for low cost and efficient materials able to emit pure colours (red, green and blue). Herein, we report amine-functionalized organic/inorganic di-ureasil hybrids consisting of a siliceous skeleton and oligopolyether chains, d-U(600), modified by distinct concentration values of a blue emitting uncharged polyfluorene (poly (9,9-dioctylfluorene)-co-phenylene) (PF). Structural and thermal studies reveal that the interaction between the PF and the d-U(600) yield to an enhancement of the PF thermal stability. The optical characterization shows that the emission is strongly dependent on the excitation energy presenting a red-shift as the excitation wavelength increases, enabling a fine tuning of the emission colour coordinates. Under UV excitation, a maximum emission quantum yield value 0.44 ± 0.04 was attained, which is remarkably higher when compared to the value found for the undoped d-U(600), 0.13 ± 0.01, an analogous to the value found for the isolated PF, pointing out that the incorporation into the hybrid host did not yield to an emission efficiency quenching. A commercial LED chip emitting at 365 nm was coated by the PF-doped d-U(600) showing a wall-plug efficiency of 0.04% and a luminous efficacy of 0.003 lm⋅W−1, demonstrating the applicability of these materials as blue-emitting phosphors to be applied in SSL.