Efficient and stable air-processed ternary organic solar cells incorporating gallium-porphyrin as electron cascade material

Two gallium porphyrins, a tetraphenyl GaCl porphyrin, termed as (TPP)GaCl, and an octaethylporphyrin GaCl porphyrin, termed as (OEP)GaCl, were synthesized to use as an electron cascade in ternary organic bulk heterojunction films. A perfect matching of both gallium porphyrins’ energy levels with that of poly(3-hexylthiophene-2,5-diyl) (P3HT) or poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) polymer donor and the 6,6-phenyl C71 butyric acid methyl ester (PCBM) fullerene acceptor, forming an efficient cascade system that could facilitate electron transfer between donor and acceptor, was demonstrated. Therefore, ternary organic solar cells (OSCs) using the two porphyrins in various concentrations were fabricated where a performance enhancement was obtained. In particular, (TPP)GaCl-based ternary OSCs of low concentration (1:0.05 vv%) exhibited a ~17% increase in the power conversion efficiency (PCE) compared with the binary device due to improved exciton dissociation, electron transport and reduced recombination. On the other hand, ternary OSCs with a high concentration of (TPP)GaCl (1:0.1 vv%) and (OEP)GaCl (1:0.05 and 1:0.1 vv%) showed the poorest efficiencies due to very rough nanomorphology and suppressed crystallinity of ternary films when the GaCl porphyrin was introduced to the blend, as revealed from X-ray diffraction (XRD) and atomic force microscopy (AFM). The best performing devices also exhibited improved photostability when exposed to sunlight illumination for a period of 8 h than the binary OSCs, attributed to the suppressed photodegradation of the ternary (TPP)GaCl 1:0.05-based photoactive film

Core-shell carbon-polymer quantum dot passivation for near infrared perovskite light emitting diodes

High-performance perovskite light-emitting diodes (PeLEDs) require a high quality perovskite emitter and appropriate charge transport layers to facilitate charge injection and transport within the device. Solution-processed n-type metal oxides represent a judicious choice for the electron transport layer (ETL); however, they don't always present suitable surface properties and energetics in order to be compatible with the perovskite emitter. Moreover, the emitter itself exhibits poor nanomorphology and defect traps that compromise the device performance. Here we modulate the surface properties and interface energetics of the tin oxide (SnO2) ETL with the perovskite emitter by using an amino functionalized difluoro{2-[1-(3,5-dimethyl-2H-pyrrol-2-ylidene-N)ethyl]-3,5-dimethyl-1H-pyrrolato-N}boron (BDP) compound and passivate the defects present in the perovskite with carbon-polymer core-shell quantum dots (PCDs) inserted into the perovskite precursor. Both these approaches synergistically improve the perovskite layer nanomorphology and enhance the radiative recombination. These properties resulted in the fabrication of near infrared (NIR) PeLEDs based on formamidinium lead iodide (FAPbI3) with a high radiance of 92 W sr-1 m-2, an external quantum efficiency (EQE) of 14% and reduced efficiency roll-off

Photochemically-induced ligand exchange reactions of ethoxy-oxo-molybdenum(V) tetraphenylporphyrin in chlorinated solvents

Photochemically-induced ligand exchange reactions of ethoxy-oxo-molybdenum (V) 5,10,15,20-tetraphenylporphyrin, Mo(V)O(TPP)-OEt, under irradiation at the Soret band region, were investigated. The reactions were performed in chlorinated solvents and followed with ultraviolet-visible spectroscopy, whereas the products were analyzed with FTIR spectroscopy, ESR spectroscopy and gas chromatography. The chloro-oxo(TPP)Mo(V) complex was obtained as the final product, where the chlorine came from the solvent. Nevertheless, these reactions were not photocatalytic, due to the photochemical inertness of the formed chloro-oxo complex, and an excess of ethanol could not initiate a new photocatalytic cycle unless water was added as well, resulting in the formation of the correspondign oxo-Mo(IV) complex. The studied photoassisted reactions of oxoMo(V) porphyrins appear attractive for possible applications in the detection of chlorinated pollutants in sensing devices, but also for the dechlorination of pollutants upon suitable optimization of processing conditions

Supramolecular Complex of a Fused Zinc Phthalocyanine-Zinc Porphyrin Dyad Assembled by Two Imidazole-C60 Units: Ultrafast Energy Transfer Followed by Electron Transfer

A new zinc phthalocyanine-zinc porphyrin dyad (ZnPc-ZnP) fused through a pyrazine ring has been synthesized as a receptor for imidazole-substituted C60 (C60Im) electron acceptor. Self-assembly via metal-ligand axial coordination and the pertinent association constants in solution were determined by 1H-NMR, UV-Vis and fluorescence titration experiments at room temperature. The designed host was able to bind up to two C60Im electron acceptor guest molecules to yield C60Im:ZnPc-ZnP:ImC60 donor-acceptor supramolecular complex. The spectral data showed that the two binding sites behave independently with binding constants similar in magnitude. Steady-state fluorescence studies were indicative of an efficient singlet-singlet energy transfer from zinc porphyrin to zinc phthalocyanine within the fused dyad. Accordingly, the transient absorption studies covering a wide timescale of femto-to-milli seconds revealed ultrafast energy transfer from 1ZnP* to ZnPc (kEnT ~ 1012 s-1) in the fused dyad. Further, a photo induced electron transfer was observed in the supramolecularly assembled C60Im:ZnPc-ZnP:ImC60 donor-acceptor complex leading to charge separated states, which persisted for about 200ns.Support from the Ministerio de Economia Industria y Competitividad of Spain (CTQ2014-55798-R and CTQ2017- 87102-R)The Special Research Account of the University of Crete,US-National Science Foundation (grant no. 1401188 to FD

STACKED OR BRIDGE STACKED POLYMERIC STRUCTURES OF METALLOPORPHYRINS AND PHTALOCYANINES INVESTIGATED BY DIFFERENCE EXAFS SPECTROSCOPY

Une extension de la technique d'analyse différentielle des spectres EXAFS a permis d'obtenir l'extinction au premier ordre des signaux intenses des macrocycles porphyriniques et donc d'observer les signaux faibles intermoléculaires qui témoignent de structures polymériques empilées, empilées mais décalées ou pontées. Cette méthode a été utilisée pour préciser la structure de phtalocyanines de nickel dopées ou non et celle d'un composé polymérique [TpTP : Ge-CrO4]n.An "extended" differential analysis of EXAFS spectra makes it possible to achieve a first order cancellation of the intense porphyrinic pattern and therefore to extract weaker intermolecular signals which give evidence for stacked, slipped-stacked or bridge-stacked polymeric structures. Recent applications of the method include structural characterizations of β-Pc : Ni, Pc : Ni/I and of a polymeric compound [TpTP : Ge-CrO4]n