Effects of Heteroatoms of Tetracene and Pentacene Derivatives on Their Stability and Singlet Fission

The effects of the introduction of an sp²-hybridized nitrogen atom (N) and thiophene ring on the structure geometries, frontier molecular orbital energies, and excited state energies related to singlet fission (SF) for some tetracene and pentacene derivatives were theoretically investigated by quantum chemical methods. The introduction of a nitrogen atom significantly decreases the energies of frontier molecular orbitals and hence improves their stabilities in air and light illumination. More importantly, it is helpful for reducing the energy loss of the exothermic singlet fission of pentacene derivatives. For fused benzene-thiophene structures, the (α, β) connection pattern could stabilize the frontier molecular orbitals, while the (β, β) connection pattern can promote the thermodynamic driving force of singlet fission. These facts provide a theoretical ground for rational design of SF materials

Correction to “Effects of Heteroatoms of Tetracene and Pentacene Derivatives on Their Stability and Singlet Fission”

Correction to “Effects of Heteroatoms of Tetracene and Pentacene Derivatives on Their Stability and Singlet Fission

Surface Decorating of CH₃NH₃PbBr₃ Nanoparticles with the Chemically Adsorbed Perylenetetracarboxylic Diimide

An organic dye-modified organolead halide CH₃NH₃PbBr₃ nanoparticle (cubic) is prepared successfully by using a perylenetetracarboxylic diimide (PDI) bearing an -NH₃⁺ headgroup as the capping ligand. The nanopartilces are homogeneous with high crystallinity. The photoluminescence of perovskite is quenched completely by the chemically adsorbed PDI molecules. This efficient fluorescence quenching has confirmed that the PDI molecules are anchored on the surface of CH₃NH₃PbBr₃ nanoparticle. The resulting nanoparticles can be dispersed in organic solvents, and the resulting dispersion remains stable for days. This result provides a general guideline for surface engineering of organolead halide CH₃NH₃PbBr₃ nanoparticles

A Covalently Linked Tetracene Trimer: Synthesis and Singlet Exciton Fission Property

A linear tetracene trimer linked by phenyl groups has been prepared for the first time. The triplet quantum yield formed via intramolecular singlet fission can reach up to 96% in this trimer, which is enhanced significantly compared with that in the dimer. This can be attributed to the stronger electronic coupling between tetracene subunits and more delocalized excitons in the trimer

Perylenetetracarboxylic Diimide Derivatives Linked with Spirobifluorene

A series of perylenetetracarboxylic diimide (PDI) compounds linked with spirobifluorene have been prepared. The orthogonal configuration of the PDI subunits efficiently hindered their molecular aggregation in solution. Energy transfer from a 1,7-diphenoxyl group substituted PDI (PO-PDI) to a 1,7-dipyrrolidinyl group substituted PDI (PY-PDI) occurred with a large efficiency when PO-PDI was selectively excited, despite the orthogonal orientation of the two units. This observation was in direct conflict with predictions derived from the Förster theory. More interestingly, this efficient energy transfer also occurred in the solid state

Synthesis and Self-Assembly of Perylenetetracarboxylic Diimide Derivatives with Helical Oligo(l‑lactic acid)_<i>n</i> Segments

Three perylenetetracarboxylic diimide (PDI) derivatives consisting of a short oligo­(l-lactic acid)_<i>n</i> (O-LLA) segment at one imide nitrogen were synthesized. The polymers were characterized by ¹H NMR and gel permeation chromatography (GPC). Their properties were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) experiments, scanning electron microscopy (SEM), electronic absorption, and circular dichroism (CD) spectroscopy. The self-assembly behavior of these PDIs in molten state as well as in solvent was examined. It was found that the structure and the morphology of the self-assembly of these polymers depend on the relative length of the O-LLA segment. The PDIs with longer O-LLA chains present liquid crystal properties with an obvious phase transition from disordered phase to an ordered (α) phase, which cannot be found for the PDIs with short O-LLA segments. The long O-LLA segments also caused a left-handed helicity for the aggregates of the PDIs from solution. This research demonstrated that one can control the order, aggregation mode, and morphology of the molecular aggregates by changing the length of the O-LLA chains. This information can be useful in the design of new organic materials that exhibit molecular aggregation

Surface Modification of Methylamine Lead Halide Perovskite with Aliphatic Amine Hydroiodide

By spin-coating method, a thin layer of dodecylamine hydroiodide (DAHI) is introduced to the surface of perovskite CH₃NH₃PbI<i>_x</i>Cl_3–<i>x</i>. This layer of DAHI successfully changes the surface of perovskite from hydrophilic to hydrophobic as revealed by the water contact angle measurement. Significantly enhanced fluorescence intensity and prolonged fluorescence lifetime are found for these modified films in comparison to those of unmodified perovskite films, suggesting that the number of structure defects is reduced dramatically. The compatibility between the perovskite and hole transfer layer (HTL) is also improved, which leads to more efficient hole collection from the perovskite layer by HTL as revealed by the fluorescence spectra, fluorescence decay dynamics, as well as the transient photocurrent measurements. Moreover, the perovskite solar cells (PSCs) fabricated from these modified perovskite films exhibit significantly improved humidity stability as well as promoted photoelectron conversion efficiency (PCE). The result of this research reveals for the first time that the layer of aliphatic amino hydroiodide is a multiple functions layer, which can not only improve the humidity stability but also promote the performance of PSCs by reducing the defect number and improve the compatibility between perovskite and HTL. Because the structure of aliphatic amines can be functionalized with myriad of other groups, this perovskite modification method should be very promising in promoting the performance of PSCs

Employing Singlet Fission into Boosting the Generation of Singlet Oxygen and Superoxide Radicals for Photooxidation Reactions

Developing highly efficient heavy-metal-free photosensitizers (PSs) for the production of reactive oxygen species (ROS) is urgent to achieve wide applications of ROS, yet it remains a great challenge. As a proof of concept, singlet fission (SF), possessing the exciton multiplication ability with a maximum 200% triplet yield, is employed to generate ROS. Herein, a metal-free tetracene dimer with a high yield (∼164%) of long-lived triplets (>300 μs) is prepared and used to generate singlet oxygen (1O2) and superoxide radicals (O2·–). Remarkably, 1O2 and O2·– yields are boosted compared to the existing traditional PSs based on intersystem crossing (ISC). The 1O2 yield reaches an unprecedented ∼148%, representing the highest value ever reported so far. Thus, this SF PS shows an improved photooxidation activity over ISC PSs. Additionally, the 1O2 and O2·– generation mechanisms are described clearly by combining TA spectra and controlled experiments. This represents the first example of utilizing the two triplet states produced by SF to generate ROS and catalyze related reactions. The work not only presents a strategy for generating and enhancing the 1O2/O2·– yield but also opens up a new field for the application of SF