Two new pincer proligands, namely 5-(p-(N,N-diphenylamino)phenylethynyl)-1,3-di(2-pyridyl)benzene (HL 1) and trans-5-(p-(N,N-diphenylamino)styryl-1,3-di(2-pyridyl)benzene (HL 2) were prepared together with their N^C^N-coordinated cyclometallated platinum(II) complexes PtL 1 X (X ¼ Cl, NCS) and PtL 2 Cl. Both ligands are intensely luminescent in solution (quantum yields > 0.8). PtL 1 X complexes display high quantum yields in solution whereas that of PtL 2 Cl is very low due to the ease with which trans to cis isomerisation of the diphenylaminostyryl C]C bond occurs. Distinct sets of emission bands attributable to the cis and trans forms are observable in glass at 77 K, the assignments being supported by TD-DFT calculations. Organic light-emitting diodes (OLEDs) have been prepared using the new compounds as phosphorescent emitters. Remarkably, despite the inferior quantum yield of PtL 2 Cl in solution, the best electroluminescence quantum efficiencies are obtained with this complex, which emerges as an excellent candidate for the preparation of NIR-OLEDs.
A switchable diode in a 2D semiconductor-molecular junction heterostructure is reported. MoS2 is exfoliated on top of a monolayer of azobenzene-substituted thiols on gold. Photoisomerization of the azobenzenes results in switching between a rectifier with rectifying ratios of 10(4) and a conductive state, as revealed by conducting atomic force microscopy.
A new multifunctional coating for photovoltaic cells incorporating light‐management, UV‐protection, and easy‐cleaning capabilities is presented. Such coating consists of a new photocurable fluorinated polymer embedding a luminescent europium complex that acts as luminescent down‐shifting (LDS) material converting UV photons into visible light. The combination of this system with ruthenium‐free organic dye‐sensitized solar cells (DSSCs) gives a 70% relative increase in power conversion efficiency as compared with control uncoated devices, which is the highest efficiency enhancement reported to date on organic DSSC systems by means of a polymeric LDS layer. Long‐term (>2000 h) weathering tests in real outdoor conditions reveal the excellent stabilizing effect of the new coating on DSSC devices, which fully preserve their initial performance. This excellent outdoor stability is attributed to the combined action of the luminescent material that acts as UV‐screen and the highly photostable, hydrophobic fluoropolymeric carrier that further prevents photochemical and physical degradation of the solar cell components. The straightforward approach presented to simultaneously improve performance and outdoor stability of DSSC devices may be readily extended to a large variety of sensitizer/luminophore combinations, thus enabling the fabrication of highly efficient and extremely stable DSSCs in an easy and versatile fashion.
Diphenyl-(4-{2-[4-(2-pyridin-4-yl-vinyl)-phenyl]-vinyl}-phenyl)-amine (DPVPA) constitutes a novel acido-triggered reversible luminescent and nonlinear optical switch. Remarkably, for the first time the Electric-Field Induced Second Harmonic generation (EFISH) technique is used to reveal a protonation-deprotonation NLO contrast.
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