Dyes and Pigments xxx (xxxx) xxx Please cite this article as: Telugu Bhim Raju, Dyes and Pigments, https://doi.org/10.1016/j.dyepig.2019.108021 Available online 9 November 2019 0143-7208/© 2019 Elsevier Ltd. All rights reserved. Effect of mono- and di-anchoring dyes based on o,m-difuoro substituted phenylene spacer in liquid and solid state dye sensitized solar cells Telugu Bhim Raju a, 1 , Jayraj V. Vaghasiya b, c, 1 , Mohammad Adil Afroz a, 1 , Saurabh S. Soni b, ** , Parameswar Krishnan Iyer a, d, * a Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India b Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar, 388 120, Gujarat, India c Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore d Center for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India A R T I C L E INFO Keywords: Mono- and di-anchor o,m-difuoro Solid state electrolyte Dye sensitized solar cell Stability ABSTRACT Novel mono- and di-anchoring organic dyes have been designed and synthesized with o,m-difuoro substituted phenylene spacer and were tested for DSSCs in presence of solid-state (SJE-4) as well as liquid (BMII) electro- lytes. The new and simple structures of Cz-D1 and Cz-D2 dyes have same carbazole donor unit with either one or two side substitution of o,m-difuoro substituted phenylene π-spacer and cyanoacrylic acid acceptor. The pho- tophysical and electrochemical properties of photosensitizes are investigated in detail and correlated with the solar cell performance. The Cz-D2 dye have ~20% higher device effciency than Cz-D1 due to its lower LUMO level, and presence of two acceptor groups which provide effcient electron extraction from carbazole donor, lesser aggregation, high molar extinction coeffcient and better charge transfer. Without using any additive, Cz- D2 exhibited an attractive power conversion effciency (PCE) of 5.35% (Jsc ¼ 10.38 mA/cm 2 , Voc ¼ 0.75 V and FF ¼ 0.60) in presence of iodide redox electrolyte. These dyes exhibit comparatively less effciency when used to fabricate a solid state dye sensitized solar cell in presence of SJE-4 electrolyte due to aggregation between fuorine substituted phenylene spacer and electrolyte through strong H-bonding that might cause more electron recombination/back electron transfer. Good stability was also observed for both the dyes. 1. Introduction To resolve the energy crisis and global environment issues alternate renewable energy sources are required to be developed [1–3]. Dye-sensitized solar cells (DSSCs) are an attractive alternative to con- ventional solar cell, because of their reasonable solar to electricity conversion effciency. Due to the high production cost of silicon solar cells, scientists are focusing on organic-materials based solar cells to replace the traditional inorganic semiconductor technologies [4–23]. Since its discovery in 1991, DSSC is fast growing technology because of low material cost, low production cost, facile fabrication process, reasonable power conversion effciency (PCE) and less environmental issues [4,5,8–20]. Typically, DSSC is an electrochemical cell consisting of a transparent conductive glass sheet (ITO/FTO) coated with a thin flm of mesoporous nano-crystalline TiO 2 as an anode and monolayer of dye molecules being used as a sensitizer, capped with a counter elec- trode and flled with electrolyte system in between the electrodes [8–20]. Extensive efforts to improve every component of DSSC to ach- ieve higher PCE have been made over the years. To date, highest PCE of >10% has been achieved with porphyrin and Ru based dyes in presence of liquid/solid electrolyte [9–13]. However, for the large scale appli- cation, these dyes are not favorable because of the high cost of “Ru” metal, tedious separation process, low molar-extinction coeffcients and environmental issues [22]. Recently, scientists have paid attention on metal-free organic dyes due to their low cost, simple preparation, easy purifcation, high molar-extinction coeffcients and environmental friendliness. The advantage of structural diversity in metal-free organic dyes allows us to easily tune optical and electrochemical properties. Although a decent PCE of ~14% has been achieved with metal-free dyes [24], investigation of novel organic dyes is still challenging and * Corresponding author. Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India. ** Corresponding author. Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar, 388 120, Gujarat, India. E-mail addresses: soni_b21@yahoo.co.in (S.S. Soni), pki@iitg.ac.in (P.K. Iyer). 1 Equal Contribution. Contents lists available at ScienceDirect Dyes and Pigments journal homepage: http://www.elsevier.com/locate/dyepig https://doi.org/10.1016/j.dyepig.2019.108021 Received 31 August 2019; Received in revised form 24 October 2019; Accepted 4 November 2019