The role of triplet excitons in enhancing polymer solar cell efficiency: a photo-induced absorption study

Inclusion of heavy metal atoms in a polymer backbone allows transitions between the singlet and triplet manifolds. Interfacial dissociation of triplet excitons constitutes a viable mechanism for enhancing photovoltaic (PV) efficiencies in polymer heterojunction-based solar cells. The PV efficiency from polymer solar cells utilizing a ladder-type poly (para-phenylene) polymer (PhLPPP) with trace quantity of Pd atoms and a fullerene derivative (PCBM) is much higher than its counterpart (MeLPPP) with no Pd atom. Evidence is presented for the formation of a weak ground-state charge-transfer complex (CTC) in the blended films of the polymer and PCBM, using photo-induced absorption (PIA) spectroscopy. The CTC state in MeLPPP:PCBM has a singlet character to it, resulting in a radiative recombination. In contrast, the CTC states in PhLPPP:PCBM are more localized with a triplet character. An absorption peak at 1.65 eV is observed in PhLPPP:PCBM blend in the PIA, which may be converted to weakly-bound polaron-pairs, contributing to the enhancement of PV efficiency.Comment: 19 pages, 11 figure

Regular and Singular Pulse and Front Solutions and Possible Isochronous Behavior in the Short-Pulse Equation: Phase-Plane, Multi-Infinite Series and Variational Approaches

In this paper we employ three recent analytical approaches to investigate the possible classes of traveling wave solutions of some members of a family of so-called short-pulse equations (SPE). A recent, novel application of phase-plane analysis is first employed to show the existence of breaking kink wave solutions in certain parameter regimes. Secondly, smooth traveling waves are derived using a recent technique to derive convergent multi-infinite series solutions for the homoclinic (heteroclinic) orbits of the traveling-wave equations for the SPE equation, as well as for its generalized version with arbitrary coefficients. These correspond to pulse (kink or shock) solutions respectively of the original PDEs. Unlike the majority of unaccelerated convergent series, high accuracy is attained with relatively few terms. And finally, variational methods are employed to generate families of both regular and embedded solitary wave solutions for the SPE PDE. The technique for obtaining the embedded solitons incorporates several recent generalizations of the usual variational technique and it is thus topical in itself. One unusual feature of the solitary waves derived here is that we are able to obtain them in analytical form (within the assumed ansatz for the trial functions). Thus, a direct error analysis is performed, showing the accuracy of the resulting solitary waves. Given the importance of solitary wave solutions in wave dynamics and information propagation in nonlinear PDEs, as well as the fact that not much is known about solutions of the family of generalized SPE equations considered here, the results obtained are both new and timely.Comment: accepted for publication in Communications in Nonlinear Science and Numerical Simulatio

Preparation Of Perovskite Pb(Mg1/3Nb2/3)03 Using Pb3Nb208 And MgO

The synthesis of perovskite Pb(Mg1/3Nb2/3)O3 from an equimolar mixture of Pb3Nb208 and MgO was studied by solid‐state reaction techniques. An addition of 1 wt% excess MgO to the stoichiometric composition enhances the formation of the cubic perovskite phase. The absence of free PbO in the initial starting materials minimizes the volatilization loss during firing, thereby reducing the possibility of any compositional change and resulting in a substantial improvement of the perovskite phase purity over the conventional mixed‐oxide processing. Copyright © 1986, Wiley Blackwell. All rights reserve

Microstructural Inhomogeneity In Sintered Pb(Mg1/3Nb2/3)O3‐PbTiO3 Based Dielectrics

The sintering behavior and microstructural development of dielectric ceramics based on Pb(Mg1/3Nb2/3)O3‐PbTiO3 solid solutions are greatly affected by the formation of a liquid phase at ∼ 1290°C. Prolonged sintering at and above this temperature gives rise to an excessive PbO loss and the resultant variation in composition leads to an inhomogeneous microstructure. The inhomogeneity is characterized by the formation of a dense, localized region containing a PbO‐rich liquid near the surface with a porous interior region in the bulk of the sample. Copyright © 1987, Wiley Blackwell. All rights reserve

Reaction During Sintering Of Barium Titanate With Lithium Fluoride

The reactions occurring during sintering of stoichiometric BaTiO3 with small additions of LiF were studied at temperatures between 700° and 900°C. BaTiO3 reacts with LiF to form a cubic solid solution and Li2TiO3 During sintering, the cubic solid solution coexists with Li2Ti03 and forms a liquid phase at 740°± 5°C. The occurrence of a liquid phase at this temperature results in an enhancement of the sintering process and leads to the development of a highly dense microstructure. Copyright © 1986, Wiley Blackwell. All rights reserve

PASTEURELLOSIS IN DUCK IN WEST BENGAL

Two hundred sixty four samples were collected from heart blood, liver, spleen and femur of 85 khaki Campbell ducks of which P. multocida could be isolated from 4 (4.70%) birds. Out of 4 samples, organisms could be isolated from heart blood of one ducklings liver and femur of one duck each. All the isolates were found positive to catalase, oxidase, indole, nitrate reduction test and negative to methyl red, Voges-Proskaur, citrate utilization, H2S production and triple sugar iron test. The isolates fermented glucose and manitol without production of gas and non-fermented lactose, salicin, dulcitol and inositol. The isolates were non-motile and pathogenic to mice. All isolates of P. multocida were sensitive to amoxiclav, chloramphenicol, gentamicin and three isolates were sensitive to co-trimoxazole. All were moderately sensitive to amikacin, cefotaxime, neomycin and norfloxacin and resistant to ciprofloxacin and lomefloxacin

Effect Of Excess PbO On The Sintering Characteristics And Dielectric Properties Of Pb(Mg1/3Nb2/3)O3–PbTiO3‐Based Ceramics

Additions of excess PbO to the perovskite Pb[(Mg1/3Nb2/3)0.92Ti0.08]O3 solid solution enhanced the formation of a liquid phase at 840°C, which served as a densification aid for the ceramics. The liquid phase allowed elimination of pores and promoted grain growth during sintering. With additions of 1 to 2 wt% excess PbO, densities in excess of 97% of theoretical were obtained at a sintering temperature of 950°C. The peak dielectric constants of the resulting ceramics were over 18 000 at 30°C and dissipation factors less than 1%. Additions of PbO in excess of 2 wt% resulted in inferior dielectric properties due mainly to the dilution of the ferroelectric phase. Copyright © 1988, Wiley Blackwell. All rights reserve