Recent Progress in Photonic Upconversion Materials for Organic Lanthanide Complexes

Abstract

Organic lanthanide complexes have garnered significant attention in various fields due to their intriguing energy transfer mechanism, enabling the upconversion (UC) of two or more low-energy photons into high-energy photons. In comparison to lanthanide-doped inorganic nanoparticles, organic UC complexes hold great promise for biological delivery applications due to their advantageous properties of controllable size and composition. This review aims to provide a summary of the fundamental concept and recent developments of organic lanthanide-based UC materials based on different mechanisms. Furthermore, we also detail recent applications in the fields of bioimaging and solar cells. The developments and forthcoming challenges in organic lanthanide-based UC offer readers valuable insights and opportunities to engage in further research endeavors.

Upconverting photons at the molecular scale with lanthanide complexes

“…The purpose of this perspective article is not to review in depth the field of molecular UC with Ln complexes, this has been thoroughly done in different recent review articles, 31–34 but rather to expound the different mechanisms affording UC at the molecular scale, their interest or drawbacks and possible directions to improve molecular UC probes.…”

Yb-to-Eu Cooperative Sensitization Upconversion in a Multifunctional Molecular Nonanuclear Lanthanide Cluster in Solution

“…In particular, the development of materials − and molecules − capable of luminescence upconversion (UC) is booming . UC is the process in which the energy from multiple incoming photons absorbed by a material or a molecule is re-emitted in the form of a single photon of higher energy than the incident light, resulting in an anti-Stokes process.…”

Symmetry and Rigidity for Boosting Erbium‐Based Molecular Light‐Upconversion in Solution

“…Under weak incident excitation power used for inducing linear upconversion in molecular complexes ( P =0.1–40 W ⋅ cm −2 ), [12,25–47] a negligible number of molecules exist in the excited levels ($${N_{{\rm{A}}{\rm{,S - S}}}^{\left| 0 \right\rangle } \approx N^{{\rm{tot}}} = 1}$$ ) and the rate constants of the excitation processes ($${k_{\rm{A}}^{{\rm{exc}}\left( {i \to j} \right)} }$$ ) are largely dominated by the relaxation rate constants ($${k_{\rm{A}}^{j \to i} }$$ ) so that (i) $${k_{\rm{A}}^{{\rm{exc}}(1 - 2)} \ll k_{\rm{A}}^{1 \to 0} }$$ and (ii) $${k_{\rm{A}}^{{\rm{exc}}\left( {1 \to 2} \right)} k_{\rm{A}}^{2 \to 0} \ll \left( {k_{\rm{A}}^{1 \to 0} } \right)\left( {k_{\rm{A}}^{2 \to 1} + k_{\rm{A}}^{2 \to 0} } \right)}$$ . The total upconversion quantum yield thus reduces to …”

“…) due to a massive increase in non-radiative relaxation processes produced by the considerable thermal vibrational bath found in molecules. [24] Consequently, the few dozens of lanthanide-containing molecular complexes displaying detectable (linear) light upconversion under weak excitation intensity powers (P � 40 W • cm À 2 ) [12,[25][26][27][28][29][30][31][32][33][34] relied mainly on ETU [35][36][37][38] or on related multicenter Cooperative Upconversion (CU) processes. [39][40][41][42][43] However, the synthetic difficulties associated with the non-statistical combination of sensitizers and activators within a single molecular entity for programming ETU or CU mechanisms, particularly when both partners are open-shell labile lanthanide cations, [33,[39][40][41][42][43] pave the way for the single-center ESA to rise as the ultimate fully controlled upconversion process programmed at the molecular level in the absence of statistical doping.…”