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The exploitation of singlet fission (SF) materials in optoelectronic devices is restricted by the limited number of SF materials available and developing new organic materials that undergo singlet fission is a significant challenge. Using new strategy based on conjugating strong donor and acceptor building blocks, we have designed and synthesized the small molecule (BDT(DPP) 2 ) and polymer (p-BDT-DPP) systems knowing that bisthiophene-2,5-Dihydropyrrolo[3,4-c]pyrrole-1,4-dione (DPP) has a low lying triplet energy level, which is further confirmed by Time-Dependent Density Functional Theory (TD-DFT) calculations. TD-This article is protected by copyright. All rights reserved. 2 DFT and natural transition orbital (NTO) analysis were conducted to gain insight into the photophysical properties and features of excited states in BDT(DPP) 2 , respectively. Femtosecond and nanosecond transient absorption spectroscopy were used to investigate the excited state kinetics in the synthesized compounds. A global target analysis (GTA) was also applied to help analyze the transient absorption data and identify the individual features. Fast formation of triplet pairs in thin film of p-BDT-DPP and BDT(DPP) 2 and the equilibrium formation of correlated triplet pairs and S 1 from triplet-triplet annihilation in solution of BDT(DPP) 2 is evidence of SF in these compounds. The short triplet lifetime, as a result of fast biexcitonic recombination pairs, provides additional support for their formation through singlet fission.

Novel enzyme-free and direct electrochemical glucose biosensors, using glassy carbon electrode modified by iron oxide nanoparticlesdecorated MWCNTs are fabricated. The MWCNTs were synthesized by catalytic chemical vapor deposition using ferrocene as a floating catalyst and functionalized in HNO 3 . The morphology and structure of the samples were characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR). The electrocatalytic activity of the modified electrode toward glucose oxidation was evaluated by cyclic voltammetery and amprometry in 0.05 M phosphate buffer solution at pH 7.0. The results show that the functionalized MWCNTs significantly enhance the catalytic behavior of Fe 3 O 4 for glucose oxidation. The direct electron transfer coefficient between the electrode surface and glucose is 0.35. The prepared electrode shows a linear behavior in the range of 0.5-7.0 mM with a high sensitivity of 238.7 μA mM −1 cm −2 and a low detection limit of 15.0 μM at S/N = 3.0. The glucose biosensor exhibits reproducible response, long-term stability, as well as no interference from ascorbic and uric acids.

Developing photostable compounds that undergo quantitative singlet fission (SF) is a key challenge. As SF necessitates electron transfer between neighboring molecules, the SF rate is highly sensitive to intermolecular coupling in the solid state. We investigate SF in thin films for a series of perylenediimide (PDI) molecules. By adding different substituents at the imide positions, the packing of the molecules in the solid state can be changed. The relationship between SF parameters and the stacked geometry in PDI films is investigated, with two-electron direct coupling found to be the main SF mechanism. Time-resolved emission and transient absorption data show that all of the PDI films undergo SF although with different rates and yields varying from 35 to 200%. The results show that PDI1 and 2, which are stacked PDI pairs twisted out of alignment along the highest occupied molecular orbital to lowest unoccupied molecular orbital transition, exhibit faster and more efficient SF up to 200% yield. We demonstrate that both triplet formation and decay rates are highly sensitive to the ordering of the molecules within a film. The results of this study will assist in the design of optimized structures with a fast SF rate and low recombination rate that are required for useful light harvesting applications.

The dominant loss mechanism in single-junction photovoltaic (PV) devices following excitation with high-energy photons is the wasted excess energy above the bandgap that is emitted as heat (thermalization losses), leading to a maximum theoretical Solution and solution-deposited thin films of the discotic liquid crystalline electron acceptor-donor-acceptor (A-D-A) p-type organic semiconductor FHBC(TDPP) 2 , synthesized by coupling thienyl substituted diketopyrrolopyrrole (TDPP) onto a fluorenyl substituted hexa-peri-hexabenzocoronene (FHBC) core, are examined by ultrafast and nanosecond transient absorption spectroscopy, and time-resolved photoluminescence studies to examine their ability to support singlet fission (SF). Grazing incidence wide-angle X-ray (GIWAX) studies indicate that as-cast thin films of FHBC(TDPP) 2 are "amorphous," while hexagonal packed discotic liquid crystalline films evolve during thermal annealing. SF in as-cast thin films is observed with an ≈150% triplet generation yield. Thermally annealing the thin films improves SF yields up to 170%. The as-cast thin films show no long-range order, indicating a new class of SF material where the requirement for local order and strong near neighbor coupling has been removed. Generation of long-lived triplets (µs) suggests that these materials may also be suitable for inclusion in organic solar cells to enhance performance.