Synergistic photoluminescence enhancement in conjugated polymer-di-ureasil organic-inorganic composites

Abstract

Poly(fluorene) conjugated polyelectrolyte (CPE)-di-ureasil organic-inorganic composites have been prepared using a versatile sol-gel processing method, which enables selective localisation of the CPE within the di-ureasil matrix. Introduction of the CPE during the sol-gel reaction leads to a homogeneous distribution of the CPE throughout the di-ureasil, whereas a post-synthesis solvent permeation route leads to the formation of a confined layer of the CPE at the di-ureasil surface. The CPE and the di-ureasil both function as photoactive components, contributing directly to, and enhancing the optical properties of their composite material. The bright blue photoluminescence exhibited by CPE-di-ureasils is reminiscent of the parent CPE; however the distinct contribution of the di-ureasil to the steady-state emission profile is also apparent. This is accompanied by a dramatic increase in the photoluminescence quantum yield to >50%, which is a direct consequence of the synergy between the two components. Picosecond time-correlated single photon counting measurements reveal that the di-ureasil effectively isolates the CPE chains, leading to emissive trap sites which have a high radiative probability. Moreover, intimate mixing of the CPE and the di-ureasil, coupled with their strong spectral overlap, results in efficient excitation energy transfer from the di-ureasil to these emissive traps. Given the simple, solution-based fabrication method and the structural tunability of the two components, this approach presents an efficient route to highly desirable CPE-hybrid materials whose optoelectronic properties may be enhanced and tailored for a targeted application.