02526nas a2200157 4500008004100000245013100041210006900172260000800241300001600249490000800265520188100273100001902154700003902173700002702212856012902239 2017 eng d00aMolecular control of the band edge movement and the recombination process in donor-acceptor hemicyanine-sensitized solar cells0 aMolecular control of the band edge movement and the recombinatio cOCT a21836-218470 v1213 aThe presence of downward shift in the band edge and the recombination reactions in the hemicyanine-sensitized solar cell reduces the open-circuit potential (V-oc) and the short-circuit current density (J(sc), which in turn decreases the dye cell performance. Choosing either an electrolyte possessing minimum overpotentials or a systematic dye design which can efficiently suppress the diffusion of charged species toward the TiO2 can improve the overall power conversion efficiency (PCE). Here, a series of donor acceptor (D-A) hemicyanine dyes were synthesized utilizing a planar heterotriangulene (HT) or triphenylamine (TPA) donor and alkyl-functionalized indolium carboxylic acid acceptor unit. By introducing strong HT donor instead of TPA, the photophysical, and electrochemical properties of D-A dyes are significantly modulated. The strong donor nature of HT and effective passivation of surface by hydrophobic alkyl chains close to the anchoring group for NC3 dye exhibits an average PCE of 4.34% with a V-oc of 0.416 V, J(sc) of 20.04 mA cm(-2), and fill factor (ff) of 52.03% under simulated AM 1.5G illumination (100 mW cm-2) without 3 alpha,7 alpha-adihydroxy-5 beta-cholic acid coadsorbent (CDCA). The intrinsic dipole of the hemicyanine dye and the presence of Li+ ions in iodide/triiodide redox couple without tert-butylpyridine (TBP) additive induces a downward shift in conduction band edge (E-CB) of TiO2. By rational molecular design, the extend of shift in E-CB is controlled and enhanced the V-oc. Electrochemical impedance spectroscopy (EIS) studies revealed the high charge transfer resistance (R-ct) and long lifetime (tau) of injected electrons in HT-based dyes than that of TPA derivatives, which provide insight into the passivation of Li+ and I- ions by current D-A dye design possessing alkyl functionalities to increase both the J(sc) and V-oc.1 aKarjule, Neeta1 aKavungathodi, Munavvar, Fairoos Me1 aNithyanandhan, Jayaraj uhttps://library.ncl.res.in/content/molecular-control-band-edge-movement-and-recombination-process-donor-acceptor-hemicyanine01911nas a2200181 4500008004100000022001400041245018500055210006900240260000900309300001200318490000700330520117100337100001801508700001801526700003001544700002701574856012801601 2018 eng d a1474-905X00aModulated photochemical reactivities of O-acetylated (3', 5'-dimethoxyphenyl) heteroaryl acyloin derivatives under direct irradiation and photo-induced electron transfer conditions0 aModulated photochemical reactivities of Oacetylated 3 5dimethoxy cJUN  a835-8450 v173 a

3', 5'-Dimethoxybenzoin esters are important photoremovable protecting groups which form 2-phenylbenzofuran derivatives upon photo-release. We utilized a similar concept to test a photochemical method of installing a benzofuran moiety to the conjugated backbone by subjecting O-acetylated (3', 5'-dimethylphenyl) heteroaryl acyloin derivatives through direct photo irradiation and a photo-induced electron transfer reaction. These photochemical methods were explored for a variety of heteroaromatic substrates appended on the ketone part of the O-acetylated cross-acyloin derivatives. The furan, thiophene and bithiophene derivatives led to the expected cyclized (benzofuran capped) products but the derivatives with extended conjugation decomposed under direct irradiation. However, under irradiation in the presence of an electron donor such as triethylamine, the extended acyloin derivatives afforded both cyclized and deacetoxylated products. The semiconducting nature of the extended cyclized products was also explored and tested for solution-processed organic field effect transistors, providing a maximum hole mobility of 1.3 x 10(-6) cm(2) V-1 s(-1).

1 aBisht, Rajesh1 aSingh, Saumya1 aKrishnamoorthy, Kothandam1 aNithyanandhan, Jayaraj uhttps://library.ncl.res.in/content/modulated-photochemical-reactivities-o-acetylated-3-5-dimethoxyphenyl-heteroaryl-acyloin01391nas a2200169 4500008004100000245009900041210006900140260000800209300001300217490000800230520076700238100001901005700002701024700002701051700001901078856012401097 2018 eng d00aModulation of reactivity of singlet radical pair in continuous flow: photo-fries rearrangement0 aModulation of reactivity of singlet radical pair in continuous f cJUN a 316-3210 v3643 a

Photo-Fries rearrangement of phenyl benzoate is studied using continuous flow for modulating the reactivity of singlet radical pair by changing the viscosity of the solvent. The effect of flow and proximity of the reactants with the light source on the reactivity of radical pair, formed from singlet excited state was investigated in details. In non-viscous solvent, the results from flow synthesis were comparable to batch reactor. In viscous solvents, selectivity of ortho- and para-isomers (o-/p- isomer) of the product could be controlled by changing viscosity as well as the flow rate. Using flow synthesis, ortho- and para-isomer ratio was obtained as high as 8.45 which are twice as compared to batch experiment with in fraction of residence time.

1 aKarjule, Neeta1 aSharma, Mrityunjay, K.1 aNithyanandhan, Jayaraj1 aKulkarni, Amol uhttps://library.ncl.res.in/content/modulation-reactivity-singlet-radical-pair-continuous-flow-photo-fries-rearrangement02030nas a2200253 4500008004100000022001400041245010900055210006900164260000800233490000600241520111800247653002201365653002701387653003101414653001701445653003201462100002701494700002401521700003401545700001801579700003001597700002701627856012201654 2023 eng d a2367-093200aModular TiO2-squaraine dyes/electrolyte interface for dye-sensitized solar cells with cobalt electrolyte0 aModular TiO2squaraine dyeselectrolyte interface for dyesensitize cAPR0 v73 a

Strategies to diminish both charge recombination and aggregation of dyes on the photoanode by functionalizing the sensitizer with alkyl groups is the best approach to achieve high dyesensitized solar cell (DSSC) efficiency. Development of such a photoanode with NIR-active dyes which is compatible with a cobalt electrolyte is important to enhance the photovoltaic performance. In this report, alkyl-group-wrapped donor-acceptor-donor (D-A-D) based unsymmetrical squaraine dyes have been used for DSSC device characterization with a cobalt electrolyte. Surface passivation of photoanode was varied systematically by the extent of functionalization with alkyl groups to avoid charge recombination. DSSC device performance of 5.92% was achieved for an alkyl-group-wrapped squaraine dye with a cobalt electrolyte. Hence, appending the alkyl groups on the donor unit of squaraine dyes helps passivating the photoanode, whereas introducing hydrophilic groups provides a leaky surface where oxidized electrolyte species reach the titanium-metal-oxide surface which promotes the charge recombination process.

10acounter-electrode10aDSSC device efficiency10aDye-sensitized solar cells10aElectrolytes10aunsymmetrical squaraine dye1 aSingh, Ambarish, Kumar1 aSudhakar, Vediappan1 aJavaregowda, Bharathkumar, H.1 aBisht, Rajesh1 aKrishnamoorthy, Kothandam1 aNithyanandhan, Jayaraj uhttps://library.ncl.res.in/content/modular-tio2-squaraine-dyeselectrolyte-interface-dye-sensitized-solar-cells-cobalt