Luminescence Tuning of MEH-PPV for Organic Electronic Applications

Abstract

In this report, a doped semiconducting ink consisting of a blended poly [2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) with aluminium-tris (8-hydroxychinolin) (Alq3) and diluted in toluene is formulated. The intentional doping with the electron transport nanoparticle Alq3 results in an additional band gap state of the hole transport MEH-PPV polymer and reduction of the switch on voltage of the organic LED display. Doping is probed at room temperature with photoluminescence spectroscopy. Photoluminescence results revealed that as the Alq3 content increases in blends, characteristic peaks of intensities of MEH-PPV are broadened and reduced. In addition, the emission for Alq3 concentrations between 30% and 60% are featured by a band at 565 nm (2.19 eV) for the lower concentration and consistently blue shifted to 530 nm (2.33 eV) for the higher concentration. This new band at 565 nm (2.19 eV) neither belongs to pure MEH-PPV nor to Alq3 and evidences charge transfer from the lowest unoccupied molecular orbital of the Alq3 to the highest occupied molecular orbital of the MEH-PPV.

Excitation Energy Transfer/Migration between Tris(8-hydroxyquinoline) Aluminum and Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] in Chloroform

“…This indicates that, as the concentration of acceptor increases in the solution, more efficient radiationless energy transfer takes place between the donor–acceptor pair. In the emission spectrum of the donor–acceptor solution, we could not observe any new emission band, which rules out the formation of exciplex of AlQ 3 -MEH-PPV in chloroform solution, which is observed in their blend …”

“…On increasing acceptor concentration, it is also evident from these spectra that In the emission spectrum of the donor−acceptor solution, we could not observe any new emission band, which rules out the formation of exciplex of AlQ 3 -MEH-PPV in chloroform solution, which is observed in their blend. 6 Further, as we increase the amount of acceptor in the solution, the contribution of energy migration due to acceptor−acceptor interaction also increases. Therefore, a successive red shift in the emission maxima corresponding to the acceptor appears on increasing the concentration of acceptor.…”

“…23 Recently, luminescence tuning in the MEH-PPV-doped AlQ 3 blend was reported by Sierra and Marulanda. 6 Their photoluminescence results revealed that, as the AlQ 3 content increases in blends, characteristic emission peaks of MEH-PPV become broader with reduced intensity. Besides, they also found an emission band at 565 nm (2.19 eV) for the lower concentration, which consistently blue-shifted to 530 nm (2.33 eV) for the higher concentration of AlQ 3 .…”

“…Recently, intense research is going on for the development of efficient organic light-emitting diode (OLED), photodetectors, optical sensors, and solar cells by using blended organic fluorescent material containing π-conjugated semiconducting polymers and organometallic molecules. − Enhancement in both fluorescence intensity and decay time in the presence of an external electric field has been observed in these π-conjugated semiconducting polymer thin films. , Use of these semiconducting polymers avoids complexity in the architecture of device fabrication through multilayer structures. Interestingly, many conjugated light-emitting polymers are hole conductive and show low electron mobility, therefore having low efficiency .…”

Statistical Properties of a Polymer Chain in the Environment with Low Concentration of Nanoparticles

“…The existence of NPs can change the dynamics of polymers and therefore shifts the glass transition temperature [14] and slows down the diffusion of polymer chains [15]. Recently, the dynamics of polymer melts and concentrated polymer solutions have been studied intensively by experiments [16,17], theory and computer simulations [18][19][20][21]. It was found that the properties of polymers would be influenced by many parameters, such as size, shape, and concentration of NPs and interaction strength between polymer and NP [10].…”