Inhibition of Energy Transfer between Conjugated Polymer Chains in Host/Guest Nanocomposites Generates White Photo- and Electroluminescence

Abstract

The generation of white light requires the combination of two or more chromophores that emit simultaneously. The observed color of a mixture of light-emitting molecules, however, originates generally only from the lowest band-gap species because of efficient energy transfer between the chromophores which is difficult to avoid. Here we report on a nanocomposite material designed to yield pure and stable white photo- and electroluminescence. In this material, red, green, and blue emitting conjugated polymers are confined within the galleries of a layered semiconducting host matrix. The host hinders polymer pi-pi interactions which are responsible for the energy transfer between polymer chains, consequently, emission from the three chromophores is observed simultaneously resulting in white photoluminescence. The efficacy of the nanocomposites is demonstrated in simple single-layer white-emitting polymer diodes. The mechanism suggested here for white light generation, supported by extensive luminescence measurements, is in contrast to that previously reported in white-emitting polymer diodes where efficient energy transfer between polymer chains was essential for obtaining white light.

Decoupling 2D Inter‐ and Intrachain Energy Transfer in Conjugated Polymers

“…The absence of the closely p-p packed polymer chains, known to be the origin of fast energy transfer in 3D films, suppresses the overall rate of energy transfer in the low-dimensional systems. [10,12] Recently, stalled energy transfer in 2D systems was utilized for the fabrication of color-controlled [13] and white-emitting PLEDs. [13,14] However, whether 2D energy transfer in conjugated polymer monolayers occurs mainly along polymer chains (intrachain) or between in-plain neighboring but noncoupled polymer chains (interchain) has yet to be determined due to the experimental difficulty of decoupling inter-and intrachain interactions in polymer monolayers.…”

“…[10,12] Recently, stalled energy transfer in 2D systems was utilized for the fabrication of color-controlled [13] and white-emitting PLEDs. [13,14] However, whether 2D energy transfer in conjugated polymer monolayers occurs mainly along polymer chains (intrachain) or between in-plain neighboring but noncoupled polymer chains (interchain) has yet to be determined due to the experimental difficulty of decoupling inter-and intrachain interactions in polymer monolayers. The aim of this study is therefore to experimentally distinguish between intra-and interchain energytransfer processes in a 2D conjugated polymer system.…”

Self-assembled lamellar MoS 2 , SnS 2 and SiO 2 semiconducting polymer nanocomposites

“…Finally, the efficacies of polymer-incorporated SnS 2 were demonstrated in a simple single-layer polymer light-emitting diode comprising the tricolour polymer blend interacted SnS 2 nanocomposites. The electroluminescence spectrum of the nanocomposite device is similar to its PL spectrum exhibiting white electroluminescence with nearly pure-white CIE coordinates (0.30, 0.30) (Aharon et al 2006b). …”

Dimensionality-dependent energy transfer in polymer-intercalatedSnS2nanocomposites

“…This strong interaction between the components makes such materials extremely sensitive to doping levels and film morphology, both of which may in turn be influenced by processing conditions and change over time. An alternative approach suggested by Aharon et al 15,16 is based on the confinement of the polymer blend in the interlayer galleries of an inorganic semiconducting material that is largely transparent over the visible spectrum. The formation of quasi-twodimensional polymer monolayers within this nanocomposite should inhibit energy transfer between the polymer blend components, allowing stable tuning of the apparent emission color though changes in the blend composition.…”

“…Using this approach, stable white-light emission has recently been demonstrated for a nanocomposite containing a blend of three polymers emitting in the blue, green, and red part of the visible spectrum. 15 The inorganic interlayers may have the additional functions of aiding charge carrier injection 15 and protecting the polymer against degradation through encapsulation.…”