Visible and NIR emitting Yb(iii) and Er(iii) complexes sensitized by β-diketonates and phenanthroline derivatives

Determining Factors to Understand the External Quantum Efficiency Values: Study Carried Out with Copper(I)-I and 1,2-Bis(4-pyridyl)ethane Coordination Polymers as Downshifters in Photovoltaic Modules

Downshifters refer to compounds with the capacity to absorb UV photons and transform them into visible light. The integration of such downshifters has the potential to improve the efficiency of commercial photovoltaic modules. Initially, costly lanthanide derivatives and organic fluorescent dyes were introduced, resulting in a heightened module efficiency. In a novel research direction guided by the same physicochemical principles, the utilization of copper(I) coordination compounds is proposed. This choice is motivated by its simpler and more economical synthesis, primarily due to copper being a more abundant and less toxic element. Our proposal involves employing 1,2-bis(4-pyridyl) ethane (bpe), an economically viable commercial ligand, in conjunction with CuI to synthesize coordination polymers: [CuI(bpe)]n(1), [Cu3I3(bpe)3]n(2), and [CuI(bpe)0.5]n(3). These polymers exhibit the ability to absorb UV photons and emit light within the green and orange spectra. To conduct external quantum efficiency studies, the compounds are dispersed on glass and then encapsulated with ethylene vinyl acetate through heating to 150 °C. Interestingly, during these procedural steps, the solvents and temperatures employed induce a phase transformation, which has been thoroughly examined through both experimental analysis and theoretical calculations. The outcomes of these studies reveal an enhancement in external quantum efficiency with [Cu3I3(bpe)3]n(2), at a cost significantly lower (between 340 and 350 times) than that associated with lanthanide DS complexes.

Exploring Ln(III)-Ion-Based Luminescent Species as Down-Shifters for Photovoltaic Solar Cells

In this work, we have compiled our research on lanthanide-based luminescent materials for use as down-shifter layers in photovoltaic (PV) mini-modules. The complexes we have prepared (C1-17), with formulas [Eu₂(phen)₂(bz)₆] (C1), [Eu₂(bphen)₂(bz)₆] (C2), [Eu(tta)₃bphen] (C3), [Eu(bta)₃pyz-phen] (C4), [Eu(tta)₃pyz-phen] (C5), [Eu(bta)₃me-phen] (C6), [Er(bta)₃me-phen] (C7), [Yb(bta)₃me-phen] (C8), [Gd(bta)₃me-phen] (C9), [Yb(bta)₃pyz-phen] (C10), [Er(tta)₃pyz-phen] (C11), [Eu₂(bz)₄(tta)₂(phen)₂] (C12), [Gd₂(bz)₄(tta)₂(phen)₂] (C13), [EuTb(bz)₄(tta)₂(phen)₂] (C14), [EuGd(bz)₄(tta)₂(phen)₂] (C15), [Eu_1.2Gd_0.8(bz)₄(tta)₂(phen)₂] (C16), and [Eu_1.6Gd_0.4(bz)₄(tta)₂(phen)₂] (C17), can be grouped into three families based on their composition: Complexes C1-6 were synthesized using Eu³⁺ ions and phenanthroline derivatives as the neutral ligands and fluorinated β-diketonates as the anionic ligands. Complexes C7-11 were prepared with ligands similar to those of complexes C1-6 but were synthesized with Er³⁺, Yb³⁺, or Gd³⁺ ions. Complexes C12-17 have the general formula [M1M2(bz)₄(tta)₂(phen)₂], where M1 and M2 can be Eu³⁺, Gd³⁺, or Tb³⁺ ions, and the ligands were benzoate (bz^-), 2-thenoyltrifluoroacetone (tta^-), and 1,10-phenanthroline (phen). Most of the complexes were characterized using X-ray techniques, and their photoluminescent properties were studied. We then assessed the impact of complexes in the C1-6 and C12-17 series on the EQE of PV mini-modules and examined the durability of one of the complexes (C6) in a climate chamber when embedded in PMMA and EVA films. This study emphasizes the methodology employed and the key findings, including enhanced mini-module efficiency. Additionally, we present promising results on the application of complex C6 in a bifacial solar cell.

Europium(III)-Doped Gadolinium(III) Complex for High-Sensitivity Temperature Sensing in the Physiological Range

A new Eu³⁺-doped Gd³⁺ complex of formula [Eu_0.0135Gd_0.9865(pta)₃me-phen] was synthesized and structurally characterized (Hpta = benzoyltrifluoroacetone, me-phen = 5-methyl-1,10-phenanthroline). The photoluminescence study revealed that when the compound was excited at RT, under a 457 nm continuous laser, the material exhibited high luminescence due to the antenna effect of the ligands, as well as a good balance between the phosphorescence from the spin-forbidden triplet (from the organic ligands), and the characteristic lanthanide f-f transitions. The ratio between the previous emissions drastically changed when the sample was heated up to 62 °C inside a tubular furnace. This ratio was investigated using the luminescence intensity ratio method, to analyze the capabilities of the sample as a temperature sensor. The relative sensitivity reached a maximum of 11.4 °C^-1 %, maintaining a detection limit below 0.15 °C for the whole temperature range.

Near Infared Circularly Polarized Luminescence From Water Stable Organic Nanoparticles Containing a Chiral Yb(III) Complex

We report the first example of very efficient NIR Circularly Polarized Luminescence (CPL) (around 970 nm) in water, obtained thanks to the combined use of a chiral Yb complex and of poly lactic‐co‐glycolic acid (PLGA) nanoparticles. [YbL(tta)₂]CH₃COO (L=N, N’‐bis(2‐pyridylmethylidene)‐1,2‐(R,R+S,S) cyclohexanediamine and tta=2‐thenoyltrifluoroacetonate) shows good CPL in organic solvents, because the tta ligands efficiently sensitize Yb NIR luminescence and the readily prepared chiral ligand L endows the complex with the necessary dissymmetry. PLGA nanoparticles incorporate the complex and protect the metal ion from the intrusion of solvent molecules, while ensuring biocompatibility, water solubility and stability to the complex. Hydrophilic NIR‐CPL optical probes can find applications in the field of NIR‐CPL bio‐assays.

Optical properties and energy transfer in KYF4:Sm3+ and KYF4:Tb3+,Sm3+ polycrystalline materials

(a) The CR channels between Sm³⁺ ions; (b) the emission process of Tb³⁺ ions and the energy transfer from Tb³⁺ ions to Sm³⁺.