Controlling the spatial distribution of electronic excitation in asymmetric D-A-D' and symmetric D'-A-D-A-D' electron donor-acceptor molecules.

Understanding how electronic energy is funnelled towards a specific location in a large conjugated molecule is of primary importance for the development of a site-specific photochemistry. To this end, we investigate here how electronic excitation redistributes spatially in a series of electron donor-acceptor (D-A) molecules containing two different donors, D and D', and organised in both linear D-A-D' and symmetric double-branch D'-A-D-A-D' geometries. Using transient IR absorption spectroscopy to probe the alkyne spacers, we show that for both types of systems in non-polar solvents, excitation remains delocalised over the whole molecule.

Unlocking the Potential of Push-Pull Pyridinic Photobases: Aggregation-Induced Excited-State Proton Transfer.

The pH effect on the photophysics of three push-pull compounds bearing dimethoxytriphenylamine (TPA-OMe) as electron donor and pyridine as electron acceptor, with different ortho-functionalization (-H, -Br, and -TPA-OMe), is assessed through steady-state and time-resolved spectroscopic techniques in DMSO/water mixed solutions and in water dispersions over a wide pH range. The enhanced intramolecular charge transfer upon protonation of the pyridinic ring leads to the acidochromic (from colorless to yellow) and acido(fluoro)chromic (from cyan to pink) behaviours of the investigated compounds. In dilute DMSO/buffer mixtures these molecules exhibited low pK values (≤3.

Molecular Tailoring of Pyridine Core-Based Hole Selective Layer for Lead Free Double Perovskite Solar Cells Fabrication.

To solve the toxicity issues related to lead-based halide perovskite solar cells, the lead-free double halide perovskite CsAgBiBr is proposed. However, reduced rate of charge transfer in double perovskites affects optoelectronic performance. We designed a series of pyridine-based small molecules with four different arms attached to the pyridine core as hole-selective materials by using interface engineering.

Near-IR absorbing 1,1,4,4-tetracyanobutadiene-functionalized phenothiazine sulfones.

Triphenylamine (TPA) substituted π-conjugated chromophores TPA1-TPA5 were designed and synthesized Pd-catalysed Sonogashira cross-coupling followed by [2 + 2] cycloaddition-retroelectrocyclization (CA-RE) reactions. The effects of acceptor 1,1,4,4-tetracyanobutadiene (TCBD) and cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD (DCNQ) units in the photophysical studies and the HOMO-LUMO energy levels of the phenothiazine sulfones TPA1-TPA5 were evaluated. The absorption spectra of chromophores TPA4 and TPA5 show a significant change due to the incorporation of DCNQ units, resulting in bathochromically shifted broad absorption in the NIR region.

Excitation Wavelength-Dependent Charge Stabilization in Highly Interacting Phenothiazine Sulfone-Derived Donor-Acceptor Constructs.

Prolonging the lifetime of charge-separated states (CSS) is of paramount importance in artificial photosynthetic donor-acceptor (DA) constructs to build the next generation of light-energy-harvesting devices. This becomes especially important when the DA constructs are closely spaced and highly interacting. In the present study, we demonstrate extending the lifetime of the CSS in highly interacting DA constructs by making use of the triplet excited state of the electron donor and with the help of excitation wavelength selectivity.