Solid state concentration quenching of organic fluorophores in PMMA

Abstract

In this study the concentration quenching phenomenon is explored for seven organic singlet emitters (Rhodamine 6G, Pyridine 2, Lumogen F Red 305, Perylene, Coumarin 102, DCM and DCJTB) in an inert host of poly(methyl methacrylate) (PMMA). Combining fluorescence lifetime and quantum yield measurements on samples of different molecular separation allows a deep decay rate analysis to be performed yielding, for each fluorophore, a monomial power law that indicates the strength and type of interaction. The fluorophores studied exhibit interactions in between that of FRET-like dipole-dipole (R(-6)) and surface-surface (R(-2)) with many lying close to that expected for surface-dipole (R(-3)) interactions. With no observed dependence on molecular structure it is concluded that the concentration quenching rate in singlet emitters follows a power law as kCQ = aR(-3.1±0.7) with aggregation expected to increase the magnitude of the observed power.

Efficient Vacuum‐Processed Light‐Emitting Diodes Based on Carbene–Metal–Amides

“…However, ≈50% of pixels displayed a large leakage current, on the order of 10 −2 mA cm −2 at forward biases below the EL turn-on. This implies that the concentration quenching observed for many OLED dopants [16,17] is largely absent in CMA1, as has previously been reported for its halide analogues. The bimodal variation in leakage current is thought to be due to inhomogeneity in the relatively rough UGH2 hole-blocking layer (RMS = 8.6 nm, see Figure S2, Supporting Information), which in some instances may allow a leakage of holes through the device.…”

“…High η EQE,EL was observed across a wide range of emissive layer concentrations, including a champion peak η EQE,EL = 23.1% for a 100-wt% (i.e., host-free) emissive layer. This implies that the concentration quenching observed for many OLED dopants [16,17] is largely absent in CMA1, as has previously been reported for its halide analogues. [5b] To investigate this, the absolute photoluminescence quantum efficiency (PLQE) [18] was measured under a flow of N 2 for the 20 and 100 wt% CMA1 films.…”

Reduced concentration quenching in a TADF-type copper(I)-emitter

“…Green and co-workers suggested a simple model based on the number density of the emitters in a film. [12] Based on the molecular mass of complex 1, this criterion is satisfied at doping concentrations of 8 w-% or more in PMMA. Yet, no concentration quenching could be detected even at very high doping concentrations.…”

“…For example, many fluorescent molecules show concentration quenching in solid state. [12] The same is true for phosphorescent materials such as iridium(trisphenylpyridine) [13] as well as most organic TADF materials [14]. The reasons for this are Dexter-and Förster-type energy transfer processes, which require a close proximity and a spectral overlap between emission and absorption spectra of different species to be effective.…”

Material gain concentration quenching in organic dye-doped polymer thin films

“…where the radiative decay time τ rad is assumed to be independent of the molecular dye density. On the other hand, the fluorescence lifetime τ f (N) is defined as the inverse of the sum of the radiative, non-radiative, and concentration quenching decay rates k R , k NR , k CQ [25] τ f (N)…”