@article {44642, title = {Fused fluorenylindolenine-donor-based unsymmetrical squaraine dyes for dye-sensitized solar cells}, journal = {ACS Applied Materials \& Interfaces}, volume = {10}, year = {2018}, month = {AUG}, pages = {26335-26347}, abstract = {

A series of four unsymmetrical squaraine dyes, XSQ1-4, were synthesized using a fused fluorenylindolenine-based donor unit for dye-sensitized solar cells (DSSCs). The fused structure of fluorenylindolenine helped in moving the absorption toward the near-infrared (NIR) region, and the two sp(3)-C centers available on this donor were utilized to incorporate out-of-plane alkyl chains in opposite directions to control the dye-dye interactions on the TiO2 surface. High extinction coefficient (epsilon \>= 10(5) M-1 cm(-1)) for absorbing NIR photons and suitable highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels with respect to the conduction band of TiO2 and electrolyte for charge injection and dye regeneration processes, respectively, make these dyes potential sensitizers for DSSCs. Introduction of branched alkyl groups in the pi-framework helped in controlling dye aggregation to reduce exciton quenching and assisted in TiO2 surface passivation to avoid the charge recombination process. Furthermore, having a naphthyl group on the indole part of the anchoring group containing segment helped to red-shift the absorption spectrum of dyes 15 nm toward the NIR region (XSQ3-4). Among all of the dyes under investigation, XSQ2 gave the best photovoltaic performance, having a short-circuit current density (J(SC)) of 13.99 mA cm(-2), open -circuit voltage (V-OC) of 0.66 V, and a fill factor (ff) of 0.71, with a device performance (eta) of 6.57\%. Electrochemical impedance spectroscopy revealed higher electron lifetime on TiO2 for XSQ2, which helps to avoid the charge recombination process.

}, keywords = {Dye-sensitized solar cells, fluorenylindolenine, H- and J-type aggregation, NIR absorption, out-of-plane alkyl groups, squaraine dyes}, issn = {1944-8244}, doi = {10.1021/acsami.8b09866}, author = {Bisht, Rajesh and Sudhakar, Vediappan and Kavungathodi, Munavvar Fairoos Mele and Karjule, Neeta and Nithyanandhan, Jayaraj} } @article {46915, title = {Nanoporous reduced graphene oxide and polymer composites as efficient counter electrodes in dye-sensitized solar cells}, journal = {ACS Applied Electronic Materials}, volume = {2}, year = {2020}, month = {MAR}, pages = {626-634}, type = {Article}, abstract = {

The introduction of an efficient and precious platinum (Pt) free counter electrode (CE) for dye-sensitized solar cells (DSSCs) is an important aspect to address. In this report, we have employed nanoporous reduced graphene oxide (PG) containing PEDOT:PSS-PG composite on FTO substrate as CEs, which have shown excellent diffusion of I-3(-), remarkable photocatalytic activity, and better device performance along with desired stability. The investigated cathode material has been prepared by mixing PGs and highly conducting PEDOT:PSS. Experimental measurements and analyses such as electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and so on indicate that PEDOT:PSS-PG is a promising cathode material for a Pt-free CE in DSSCs. EIS indicates that the PEDOT:PSS-PGs have lower interfacial charge-transfer resistance because of their high electrical conductivity and superior electrocatalytic activity. The achieved photoconversion efficiency (eta) of a DSSC employing the Pt-free PEDOT:PSS-PG/FTO CE is 9.57\%, which is found to be comparable to that of Pt/FTO CE based DSSC (9.64\%) under a simulated solar light illumination of 100 mW/cm(2).

}, keywords = {counter electrode, Dye-sensitized solar cells, electrocatalytic activity, PEDOT:PSS, Reduced graphene oxide}, issn = {2637-6113}, doi = {10.1021/acsaelm.9b00593}, author = {Sudhakar, Vediappan and Singh, Anup Kumar and Chini, Mrinmoy Kumar} } @article {49137, title = {Modular TiO2-squaraine dyes/electrolyte interface for dye-sensitized solar cells with cobalt electrolyte}, journal = {Chemphotochem}, volume = {7}, year = {2023}, month = {APR}, type = {Article}, abstract = {

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.

}, keywords = {counter-electrode, DSSC device efficiency, Dye-sensitized solar cells, Electrolytes, unsymmetrical squaraine dye}, issn = {2367-0932}, doi = {10.1002/cptc.202200171}, author = {Singh, Ambarish Kumar and Sudhakar, Vediappan and Javaregowda, Bharathkumar H. and Bisht, Rajesh and Krishnamoorthy, Kothandam and Nithyanandhan, Jayaraj} }