Simultaneous Two-Photon Excited Fluorescence and One-Photon Excited Phosphorescence from Single Molecules of an Organometallic Complex Ir(ppy)₃

Abstract

We report a study of excited-state lifetimes of the phosphorescent organometallic complex Ir(ppy)3 on ensemble and a single-molecule level. With decreasing concentration, an increasingly intense fast component of 3 ns lifetime appears next to the 1.1 mus phosphorescence. Experimental evidence suggests that strong two-photon absorption followed by fluorescence is responsible for the fast lifetime component.

Effect of ligands in two-photon excited luminescence of organometallic iridium complexes

“…F and P were determined from the pre-exponential coefficients obtained by two-component fitting of the decays. The ratio F/P increases rapidly for concentrations below 10 À5 M. The phenomenon is very similar to that observed before on Ir(ppy) 3 [6]. For comparison, we have included in Fig.…”

“…At the bulk concentration level of 5 Â 10 À3 M ( Fig. 2(a), top trace) the luminescence decay is exponential with a decay time of 1.02 ms, similar to that usually observed for Ir(ppy) 3 [6]. In lower concentration samples the decay is accompanied with a fast component of 3-4 ns lifetime.…”

“…The high emission quantum yield and short luminescence lifetime enabled the study of several phosphorescent organometallic complexes on a single-molecule level [2][3][4][5]. Recently, we used a timeresolved technique to measure the excited-state lifetime of Ir(ppy) 3 molecules on ensemble and single-molecule level [6]. The results reveal that at low concentrations strong two-photon absorption (TPA) gives rise to fast ns transitions coexisting with the slow phosphorescence.…”

Controlling the Radiative Rate of Deep‐Blue Electrophosphorescent Organometallic Complexes by Singlet‐Triplet Gap Engineering

“…To date, only a few reports have demonstrated the detection of light emission from higher-lying singlet states. [28][29][30] We recently succeeded in observing singlet emission from a platinum-porphyrin complex. In this case, so-called E-type (named after eosin) delayed fluorescence (i.e., thermally activated T 1 ) S 1 back-transfer) was observed to increase as a function of the ensemble temperature, opening the possibility for applications such as nanoscale molecular thermometry.…”

Single‐Molecule Electroluminescence of a Phosphorescent Organometallic Complex

“…[12][13][14][15] The heavy metals in organometallic complexes cause shortening of the triplet excitedstate lifetime to a few microseconds and an increase in the phosphorescence quantum efficiency, [16] enabling the PL study of several organometallic complexes at the single-molecule level. [17][18][19][20] The EL process on the level of a single dopant entity has been observed for colloidal quantum dots, [21,22] silver clusters [23] and carbon nanotubes.[24] Also, electric-field-induced chemiluminescence in single conjugated polymer nanoparticles has been reported recently.[25] Herein, we have succeeded in detecting the EL signal from single molecules of an organic dye doped at a very low concentration in a non-conjugated polymer host matrix. The single-molecule EL detection was possible because 1) charge recombination in the host is localized in distinct sites, 2) the onset voltage for EL of the dopant molecules is lower than that for the host and 3) the dopant molecules could be separated from the host EL background spectrally.…”