• Bijitha Balan

      Articles written in Journal of Chemical Sciences

    • Thiophene-bithiazole based metal-free dye as DSSC sensitizer: Effect of co-adsorbents on photovoltaic efficiency

      Jayanthy S Panicker Bijitha Balan Suraj Soman Tanwistha Ghosh Vijayakumar C Nair

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      A new molecule consisting of a bithiazole chromophore sandwiched between two thiophenes, functionalized with benzothiophene unit at one end and cyanoacrylic acid at the other end (BT1) was synthesized, photophysical properties were studied and employed as a photosensitizer in dye-sensitized solar cells (DSSCs). The molecule exhibited an intense absorption in the UV-visible region with absorption extending up to 500 nm. The ground and excited state potentials of BT1 were calculated to be 1.29 and -0.65 V, respectively vs. NHE using cyclic voltammetry. The ground state energy level is more positive than the triiodide electrolyte and excited state energy level is considerably more negative than the TiO2 satisfying the energetic requirements for a photosensitizer in DSSC. The solar cells fabricated from BT1 exhibited an efficiency of 1.13%. The effect of various co-adsorbents (CDCA, TP1 and TP2) on the DSSC performance was investigated in detail. In the presence of CDCA, the photovoltaic efficiency was enhanced to 1.25%, whereas, in the presence of TP1 and TP2, the efficiency lowered to 0.20% and 0.59%, respectively. The increased efficiency in the presence of CDCA could be attributed to the prevention of the aggregation of dye molecules induced by CDCA. On the other hand, TP1 and TP2 were found to be not as effective as CDCA to prevent aggregation leading to the lowering of photoconversion efficiency.

    • Self-assembly and photoinduced electron transfer in a donor β-cyclodextrin-acceptor supramolecular system

      RETHEESH KRISHNAN SUMESH BABU KRISHNAN BIJITHA BALAN KARICAL RAMAN GOPIDAS

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      Equimolar amounts of native β-cyclodextrin (β-CD), pyrene-linked adamantane (PYAD) and tert-butylpyromellitic diimide (PMDI) when dissolved in water self-assembled to form the supramolecular donor-acceptor system PYAD⊐β-CD>PMDI. The high affinity of adamantane derivatives for inclusion bindingin the β-CD cavity and the propensity of PMDI to undergo rim-binding at the narrow rim of β-CD led to the formation of PYAD⊐β-CD>PMDI. The ternary complex PYAD⊐β-CD>PMDI was thoroughly characterized using various spectroscopic techniques. β-CD performs three functions in the self-assembled complex: (1) encapsulate the adamantane unit and keep the pyrene (PY) moiety above the secondary rim, (2) rim-bind PMDI and keep it at the primary rim, and (3) act as a spacer between pyrene and PMDI. Thus, the ternary complex canfunction as a donor-spacer-acceptor system capable of undergoing photoinduced electron transfer (PET). Upon excitation of the pyrene moiety in PYAD⊐β-CD>PMDI an electron is transferred from the excited pyrene tothe PMDI ground state. Steady state and time resolved fluorescence experiments were carried out to study the PET in PYAD⊐β-CD>PMDI. Existence of the ternary system and PET processes taking place within it are further supported by laser flash photolysis experiments.

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