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Sharma G.D.,nter for Engineering and Science | Panda M.K.,University of Crete | Roy M.S.,Defence Laboratory | Mikroyannidis J.A.,University of Patras | And 2 more authors.
Journal of Renewable and Sustainable Energy | Year: 2013

A step wise approach for co-sensitization of a zinc porphyrin sensitizer (Zn-por) with symmetrical BF2-azopyrrole dye (BF2) for dye sensitized solar cells (DSSCs) has been developed. With this approach, the co-sensitized Zn-por BF2 based DSSC shows both Jsc and Voc significantly enhanced in relation to their individual sensitized DSSCs. Upon optimization, the DSSC sensitized with Zn-por BF2 system yields Jsc 12.4 mA cm-2, Voc 0.72 V, FF 0.70, and PCE 6.25. This performance is superior to that of individual DSSC sensitized with Zn-por (PCE 4.83) and BF2 (PCE 3.26), respectively, under similar conditions. The broader IPCE spectra of the DSSC based on Zn-por BF 2 dye relative to other DSSCs are responsible for the higher J sc. From the electrochemical impedance spectroscopy (EIS) data, we found that the charge recombination can be significantly retarded for co-sensitized system, relative to the Zn-por based DSSCs to account for the enhanced Voc. The PCE is further enhanced by employing decoxycholic acid (DCA) as coadsorbent. The highest PCE obtained for DSSC with Zn-por and BF2 in the presence of DCA is about 7.46. © 2013 American Institute of Physics.

Singh M.,Maulana Azad National Institute of Technology | Kurchania R.,Maulana Azad National Institute of Technology | Pockett A.,University of Bath | Ball R.J.,University of Bath | And 3 more authors.
Indian Journal of Physics | Year: 2015

The optical, electrochemical and density functional theory molecular simulation of a metal-free D-(π-A)2, i.e., 3,3′-(5,5′-(9-hexyl-9H-carbazole-3,6-diyl)bis(thiophene-5,2-diyl))bis(2-cyanoacrylic acid) denoted as D has been investigated. A stepwise cosensitization of D with N719 dye is adopted to enhance the power conversion efficiency of dye-sensitized solar cells. The metal-free dye possesses strong absorption in the 370–450 nm wavelength range and effectively overcomes the competitive light absorption by I3 −/I−. The N719/D cosensitized dye-sensitized solar cell shows a power conversion efficiency of about 7.24 %, which is higher than the dye-sensitized solar cells based on either N719 (5.78 %) or D (3.95 %) sensitizers. The improved power conversion efficiency of the cosensitized dye-sensitized solar cell is attributed to the combined enhancement of both short-circuit photocurrent and open-circuit voltage. The short-circuit photocurrent improvement is attributed to the increase in the both light-harvesting efficiency of the cosensitized photoanode and charge collection efficiency of the dye-sensitized solar cell. However, the open-circuit voltage is improved due to better adsorption and surface coverage of TiO2 on cosensitization and an associated reduction in the back electron recombination with increased electron lifetime. These effects are analyzed using electrochemical impedance spectroscopy and dark current–voltage measurements of the dye-sensitized solar cells. © 2015, Indian Association for the Cultivation of Science.

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