Highly Efficient Light-Harvesting System Based on a Phosphorescent Acceptor Coupled with Dendrimer Donors via Singlet−Singlet and Triplet−Triplet Energy Transfer

Abstract

A series of efficient light-harvesting systems (FIr3mGx, x = 1−3) based on dendrimer donor (mCP: N,N‘-dicarbazolyl-3,5-benzene) derivatives coupled with a sky blue phosphorescent acceptor (FIrpic: iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C 2‘]-3-hydroxypicolinate derivative) were prepared, and their photophysical properties were investigated. The light-harvesting ability of FIr3mGx (x = 1−3) increases with the number of energy donor mCP units. The acceptor PL intensity of the donor−acceptor conjugate dendrimers (FIr3mGx, x = 1−3) increases over 6 times with the number of mCP units via sensitization from the light-harvesting antenna after excitation at the donor absorption (λex = 310 nm), as compared to that of only an acceptor without a donor (FIrpic) upon excitation at the MLCT region (λex = 380 nm) because of efficient intramolecular singlet−singlet and triplet−triplet energy transfer from the donor to the acceptor and less luminance quenching induced by the bulky dendrimer structure. The singlet−singlet intramolecular energy transfer in FIr3mGx from the dendrimer donor to the acceptor exhibits a high efficiency of greater than 90% via the steady-state PL method and 94% via the transient PL method. Additionally, the triplet−triplet energy transfer efficiency via the transient PL method exhibits an efficiency greater than 99%. This indicates that FIr3mGx exhibits good light-harvesting abilities because the mCP unit is an efficient light absorber and because the core FIrpic functions as a spatial energy concentrator that drains energy from the dendrimer donor.

Novel iridium complex with carboxyl pyridyl ligand for dye-sensitized solar cells: High fluorescence intensity, high electron injection efficiency?

“…Chloro-bridged dimer complex [50] (0.1 mmol) and pyridine-2, 5-dicarboxylic acid (0.11 mmol) were added in a mixture of Na 2 CO 3 (88.8 mg, 0.83 mmol), and 2-ethoxyethanol (10 mL). After refluxed for 24 h under argon atmosphere, the solution was cooled to room temperature and poured into water.…”

Dendrimers: A Mimic Natural Light‐Harvesting System

“…Hong and co-workers reported an emissive light-harvesting system based on a phosphorescent core (an iridium complex) coupled with donors (N,N'-dicarbazolyl-2,3-benzene) through the poly(benzyl ether) dendritic linker. [36] Upon excitation of the outer donor, an efficient singlet-singlet energy transfer (with efficiency over 90 %) and a triplet-triplet energy transfer (with efficiency over 99 %) from the donor to the core acceptor were observed. This led to an evidently enhanced luminescence of the iridium complex core implying the application of this system in organic lightemitting materials.…”

Synthesis, Photophysical, Electrochemical Studies, and Antioxidant Properties of Fluorescein‐Linked Glycodendrimers

“…The fluorescencei ntensity of the glycodendrimers increases as the dendrimer generation increases, which is consistent with the increased number of triazolyl units along with the fluorophoricu nit, which is otherwise knowna st he valency effect in dendrimer chemistry. [20] Lifetime decay analysis was carried out on all the fluorescent glycodendrimers 1, 2, 3,a nd 4 by using the IBH time-correlated single photon counting (TCSPC) technique on excitation at 460 nm in CH 2 Cl 2 as solvent. The fluorescence decay fits ab iexponential shape with lifetimes t 1 and t 2.…”