Phosphorescence Quenching by Conjugated Polymers

Abstract

Energy transfer between phosphors and conjugated polymers was investigated using a fluorene trimer (F3) as a model conjugated material. The phosphors studied were bis-cyclometalated iridium complexes (FP, PPY, BT, PQ, and BTP), with triplet energies of 2.6, 2.4, 2.2, 2.1, and 2.0 eV, respectively (based on phosphorescence spectra). Stern-Volmer analysis of luminescent quenching shows that energy transfer from either FP or PPY to F3 is an exothermic process with Stern-Volmer quenching constants (kqSV) of near 109 M-1 s-1 while energy transfer from BT, PQ, and BTP is endothermic (kqSV = 107-106 M-1 s-1). On the the basis of above results, the triplet energy of F3 is estimated to be less than 2.3 eV (530 nm). This study suggests that conjugated polymers, which typically have lower T1 energies than F3, should also quench phosphorescent emission in thin films and organic light-emitting diodes (OLEDs) incorporating these and related phosphorescent dopants.

Solution-Processed Blue/Deep Blue and White Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) Hosted by a Polysiloxane Derivative with Pendant mCP (1,3-bis(9-carbazolyl)benzene)

“…[1][2][3][4][5][6][7][8][9] However, for high performance it is necessary to blend the triplet emitters into host matrixes to prevent self-quenching and triplet-triplet annihilation. 10,11 Recently, high external quantum efficiency over 25% has been achieved for blue and white phosphorescent OLEDs using small-molecule hosts. [12][13][14][15] However, complicated co-evaporation techniques and precise processing controls are required for small-molecule based devices to ensure high reproducibility for commercialization of the product.…”

“…11 In addition, to avoid phase separation upon heating, the host material should be thermally, electrochemically, and morphologically stable and form good quality films. 29,30 Furthermore, a larger HOMO-LUMO energy gap (E g ) than the phosphorescent guest is required to ensure direct charge trapping on the emitter.…”

In situ measurement of exciton energy in hybrid singlet-fission solar cells

“…However it is unclear that these energies are relevant to ionization at a polycrystalline pentacene heterojunction. More broadly, it would be beneficial to examine the energy of non emissive states 27 under photovoltaic operating conditions 28 , but a tunable probe of this kind is lacking.…”

Polymer OLED White Light Development Program

“…It should be noted here that the triplet energy levels of TFB are in the range of 2.2-2.3 eV, much lower than the triplet energy level estimated from the peak photoluminescence emission maximum of Ir(mppy) 3 at 2.44 eV. Thus, one might expect that TFB can quench the light emission of the PHOLED [12,13]. In this case, quenching effects were not seen because the improved hole injection resulted in the moving of the recombination zone away from the anode.…”

“…Encasing nanoparticles in organic capping molecules has been tried to achieve an optimum balance between quenching and acceleration of the radiative processes of the emissive states. A nearly two fold increase of luminance efficiency of slow phosphorescence (2,3,7,8,12,13,17,18-Octaethyl-21H,23H-porphine platinum (II) based OLEDs (around 10 microsecond emission lifetime) has been reported by blending into the PHOLED LEP thiol-capped gold nano-particles [26]. However accelerating the radiative properties of faster phosphorescence emitters such as the currently used Iridium based compounds with 1 microsecond emission lifetime, is not straightforward and capping of the metal nano-particles is not a well known procedure.…”