Oxygen reduction reaction (ORR) is increasingly being studied in oxide systems due to advantages ranging from cost effectiveness to desirable kinetics. Oxygen-deficient oxides like brownmillerites are known to enhance ORR activity by providing oxygen adsorption sites. In parallel, nitrogen and iron doping in carbon materials, and consequent presence of catalytically active complex species like C-Fe-N, is also suggested to be good strategies for designing ORR-active catalysts. A combination of these features in N-doped Fe containing brownmillerite can be envisaged to present synergistic effects to improve the activity. This is conceptualized in this report through enhanced activity of N-doped CaFeO brownmillerite when compared to its oxide parents. N doping is demonstrated by neutron diffraction, UV-vis spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. Electrical conductivity is also found to be enhanced by N doping, which influences the activity. Electrochemical characterization by cyclic voltammetry, rotating disc electrode, and rotating ring disk electrode (RRDE) indicates an improved oxygen reduction activity in N-doped brownmillerite, with a 10 mV positive shift in the onset potential. RRDE measurements show that the compound exhibits 4-electron reduction pathways with lower HO production in the N-doped system; also, the N-doped sample exhibited better stability. The observations will enable better design of ORR catalysts that are stable and cost-effective.

Copolymers of 4,4-difluoro-4-borata-3a-azonia-4a-aza-s-indacene (BODIPY) and diketopyrrolopyrrole (DPP) were synthesized. The BODIPY has a permanent dipole and the DPP has a quadrupole. The dipole and the quadrupole in the monomers are expected to bring the polymers closer and to improve the charge-transport properties. By judicious choice of these monomers, the electron wave function is evenly distributed through the molecules. However, we notice that the torsional angle at the connecting point of BODIPY and DPP is a function of the methyl moieties at the β, β′ position of the BODIPY. We found that the polymer comprising DPP and BODIPY without methyl moiety at β, β′ position showed a torsional angle of 27°, the lowest among the three polymers studied in this work. The absorption spectrum of the polymer showed transitions because of vibronic coupling indicating linearity along the polymer backbone. The band gap of the polymer was found to be 1.2 eV. The thermally stable polymer showed an ambipolar charge transport of 0.01 cm2/(V s).

The first application of the diselenolodiselenole (C4Se4) heterocycle as an active organic field effect transistor materials is demonstrated here. C4Se4 derivatives (2a-2d) were obtained by using a newly developed straightforward diselenocyclization protocol, which includes the reaction of diynes with selenium powder at elevated temperature. C4Se4 derivatives exhibit strong donor characteristics and planar structure (except 2d). The atomic force microscopic analysis and thin-film X-ray diffraction pattern of compounds 2a-2d indicated the formation of distinct crystalline films that contain large domains. A scanning electron microscopy study of compound 2b showed development of symmetrical grains with an average diameter of 150 nm. Interestingly, 2b exhibited superior hole mobility, approaching 0.027 cm(2) V(-1) s(-1) with a transconductance of 9.2 μS. This study correlate the effect of π-stacking, Se···Se intermolecular interaction, and planarity with the charge transport properties and performance in the field effect transistor devices. We have shown that the planarity in C4Se4 derivatives was achieved by varying the end groups attached to the C4Se4 core. In turn, optoelectronic properties can also be tuned for all these derivatives by end-group variation.

Organic photovoltaics (OPVs) presents an opportunity for low cost energy generation and niche applications such as collapsible electronics, solar sails, and weather resistant and curved solar roofs. [1] In recent years, OPV device performance has been consistently improving with recent power conversion efficiencies (PCEs) greater than 18%. [2,3] Unfortunately, these devices rely almost exclusively on materials that are synthetically challenging to produce and have limited large-scale potential. [4] In addition, the most promising OPV devices are fabricated by spin-coating with small active areas (<0.07 cm 2 ). While spin coating is an inexpensive and reproducible thin-film processing technique, it is very wasteful and does not scale to roll-to-roll (R2R) processes. Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7 diyl2,5thiophenediyl]: [6,6]phenyl C 71 butyric acid methyl ester (PCDTBT:PC 71 BM)-based bulk heterojunction (BHJ) OPV have been found to strike a balance between high stability, low cost, ease of synthesis, and ease of large-scale manufacturing. [5,6] Unfortunately, the performance of PCDTBT:PC 71 BM-based OPV is limited by the poor absorption of the active layer in the NIR region. This issue can be addressed using a ternary additive, as has been effectively demonstrated with some other BHJ systems. [7,8] For example, silicon phthalocyanines (SiPc) are synthetically simple conjugated macrocycles that are chemically stable and absorb light in the NIR region. SiPcs have found application in n-type organic thin-film transistors [9,10] organic light-emitting diodes [11][12][13] and recently as nonfullerene acceptors and/or ternary additives in poly(hexyl thiophene) (P3HT)-based OPVs. [14][15][16] Originally proposed by Honda et al. [17,18] and others, [19] it was determined that the addition of as little as 3-10 wt% of bis(tri-n-hexylsilyl oxide) silicon phthalocyanine ((3HS) 2 -SiPc) would increase the photocurrent generation in the 685 nm range resulting in an increase in short circuit current ( J SC ) and PCE of up to 25 and 20%, respectively, for a P3HT/PC 61 BM-based OPV device. The authors found that at low additive loadings the (3HS) 2 -SiPc would migrate to the P3HT/PC 61 BM interface providing an energy cascade between the P3HT and the PC 61 BM but when the additive loading increased the (3HS) 2 -SiPc would crystalize and form its own phase leading to a drop in device performance. [20][21][22] Recently, Vebber et al. demonstrated that matching the solubility of the SiPc additive with that of the P3HT leads to optimized OPV performance further emphasizing the subtle

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