Smoothing the energy transfer pathway in quasi-2D perovskite films using methanesulfonate leads to highly efficient light-emitting devices

Quasi-two-dimensional (quasi-2D) Ruddlesden–Popper (RP) perovskites such as BA2Csn–1PbnBr3n+1 (BA = butylammonium, n > 1) are promising emitters, but their electroluminescence performance is limited by a severe non-radiative recombination during the energy transfer process. Here, we make use of methanesulfonate (MeS) that can interact with the spacer BA cations via strong hydrogen bonding interaction to reconstruct the quasi-2D perovskite structure, which increases the energy acceptor-to-donor ratio and enhances the energy transfer in perovskite films, thus improving the light emission efficiency. MeS additives also lower the defect density in RP perovskites, which is due to the elimination of uncoordinated Pb2+ by the electron-rich Lewis base MeS and the weakened adsorbate blocking effect. As a result, green light-emitting diodes fabricated using these quasi-2D RP perovskite films reach current efficiency of 63 cd A−1 and 20.5% external quantum efficiency, which are the best reported performance for devices based on quasi-2D perovskites so far.

Intermolecular vibrational energy transfer enabled by microcavity strong light–matter coupling

Selective vibrational energy transfer between molecules in the liquid phase, a difficult process hampered by weak intermolecular forces, is achieved through polaritons formed by strong coupling between cavity photon modes and donor and acceptor molecules. Using pump-probe and two-dimensional infrared spectroscopy, we found that the excitation of the upper polariton, which is composed mostly of donors, can efficiently relax to the acceptors within ~5 picoseconds. The energy-transfer efficiency can be further enhanced by increasing the cavity lifetime, suggesting that the energy transfer is a polaritonic process. This vibrational energy-transfer pathway opens doors for applications in remote chemistry, sensing mechanisms, and vibrational polariton condensation.

Coexistence of Förster and Dexter Energy Transfer Pathways from an Antenna Ligand to Lanthanide Ion in Trivalent Europium Complexes through Phosphine-Oxide Bridges

<br>Trivalent europium (Eu3+) complexes are attractive materials for luminescence applications if energy transfer from antenna ligands to the lanthanide ion is efficient. However, the microscopic mechanisms of the transfer remain elusive and fundamental physical chemistry questions still require answers. We track the energy transfer processes in a luminescent complex Eu(hfa)3(DPPTO)2 (hfa: hexafluoroacetylacetonate, DPPTO: 2-diphenylphosphoryltriphenylene) using time-resolved photoluminescence spectroscopy. In addition to the conventional Dexter-type energy transfer pathway through the T1 state of the ligands, we discovered the Forster energy transfer pathway from the S1 of the DPPTO ligands to the 5D1 state of Eu3+ through the weak electronic interaction of a phosphine-oxide bridge. The short timescale of the energy transfer (16 ns, 127 ns) results in its high quantum yield. The coexistence of the distinct energy transfer pathways from a single chromophore is important for establishing design strategies of luminescent complexes. <br>

Coexistence of Förster and Dexter Energy Transfer Pathways from an Antenna Ligand to Lanthanide Ion in Trivalent Europium Complexes through Phosphine-Oxide Bridges

<br>Trivalent europium (Eu3+) complexes are attractive materials for luminescence applications if energy transfer from antenna ligands to the lanthanide ion is efficient. However, the microscopic mechanisms of the transfer remain elusive and fundamental physical chemistry questions still require answers. We track the energy transfer processes in a luminescent complex Eu(hfa)3(DPPTO)2 (hfa: hexafluoroacetylacetonate, DPPTO: 2-diphenylphosphoryltriphenylene) using time-resolved photoluminescence spectroscopy. In addition to the conventional Dexter-type energy transfer pathway through the T1 state of the ligands, we discovered the Forster energy transfer pathway from the S1 of the DPPTO ligands to the 5D1 state of Eu3+ through the weak electronic interaction of a phosphine-oxide bridge. The short timescale of the energy transfer (16 ns, 127 ns) results in its high quantum yield. The coexistence of the distinct energy transfer pathways from a single chromophore is important for establishing design strategies of luminescent complexes. <br>

Reverse photoluminescence responses of Ln(iii) complexes to methanol vapor clarify the differentiated energy transfer pathway and potential for methanol detection and encryption

A VOC detection and optical encryption model based on the uncommon reverse photoluminescence response of isomorphic Eu(iii) and Tb(iii) complexes to MeOH vapor.

Structure of a C2S2M2N2-type PSII–LHCII supercomplex from the green alga Chlamydomonas reinhardtii

Photosystem II (PSII) in the thylakoid membranes of plants, algae, and cyanobacteria catalyzes light-induced oxidation of water by which light energy is converted to chemical energy and molecular oxygen is produced. In higher plants and most eukaryotic algae, the PSII core is surrounded by variable numbers of light-harvesting antenna complex II (LHCII), forming a PSII–LHCII supercomplex. In order to harvest energy efficiently at low–light-intensity conditions under water, a complete PSII–LHCII supercomplex (C2S2M2N2) of the green alga Chlamydomonas reinhardtii (Cr) contains more antenna subunits and pigments than the dominant PSII–LHCII supercomplex (C2S2M2) of plants. The detailed structure and energy transfer pathway of the Cr-PSII–LHCII remain unknown. Here we report a cryoelectron microscopy structure of a complete, C2S2M2N2-type PSII–LHCII supercomplex from C. reinhardtii at 3.37-Å resolution. The results show that the Cr-C2S2M2N2 supercomplex is organized as a dimer, with 3 LHCII trimers, 1 CP26, and 1 CP29 peripheral antenna subunits surrounding each PSII core. The N-LHCII trimer partially occupies the position of CP24, which is present in the higher-plant PSII–LHCII but absent in the green alga. The M trimer is rotated relative to the corresponding M trimer in plant PSII–LHCII. In addition, some unique features were found in the green algal PSII core. The arrangement of a huge number of pigments allowed us to deduce possible energy transfer pathways from the peripheral antennae to the PSII core.

Carbon-Heteroatom Cross-Coupling via an Electronically Excited Nickel (II) Complex

<div>While carbon-heteroatom cross coupling reactions have been extensively studied, many methods are specific and</div><div>limited to a set of substrates or functional groups. Reported here is a method that allows for C-O, C-N and C-S cross coupling reactions under one general methodology. We propose that an energy transfer pathway, in which an iridium photosensitizer produces an excited nickel (II) complex, is responsible for the key reductive elimination step that couples aryl halides to 1° and 2° alcohols, anilines, thiophenols, carbamates and sulfonamides.</div>