Influence of m-fluorine substituted phenylene spacer dyes in dye-sensitized solar cells Telugu Bhim Raju a , Jayraj V. Vaghasiya b , Mohammad Adil Afroz a , Saurabh S. Soni b, ** , Parameswar Krishnan Iyer a, c, * 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 Center for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India article info Article history: Received 26 July 2016 Received in revised form 28 September 2016 Accepted 13 October 2016 Keywords: Dye sensitized solar cells meta-Fluorine substituted phenyl spacer Cyanoacrylic acid Carbazole derivatives N-containing donors abstract A series of new organic dyes based on fluorine substituted phenyl moiety, used as a p-linker in various dyes, were designed and synthesized for dye sensitized solar cell (DSSC) application. These dyes share same anchoring group (Cyano acrylic acid) with different donors such as carbazole, thiopene substituted carbazole, triphenylamine and phenothiazine moieties. For effective electron flow, the dyes were incorporated with novel D-p-A or D-A-A framework. The optical, electrochemical, time-resolved pho- toluminescence (TRPL) spectra and photovoltaic properties of the dyes were carefully studied. The results reveal that without addition of any co-adsorbent, among all fluoro-phenyl spacer dyes, the Cz-dye showed highest open circuit voltage (V oc ), short circuit current (J sc ) and exhibited enhanced PCE value of 4.2 (±0.2) %, due to the deeper HOMO level of dye, planarity of backbone with better charge transfer occurring form D to A. The optimization calculations for the geometries of all the dyes with fluoro phenyl substituted p-linkers were ascertained by Density functional theory (DFT) using B3LYP/631G (d,p) basis set. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Due to the growing demand for green energy, researchers have been attracted towards sustainable energy resources and thereby a great deal of attention on efficient solar cells development is under investigation. DSSCs with remarkable performance initially devel- oped by Gr€ atzel and O'Regan have generated immense hope in harvesting solar energy [1]. Over the past decade unconventional solar cells have been developed, yet considerable efforts on developing efficient dye sensitized solar cell (DSSC) have been devoted due to the high solar energy to electric conversion effi- ciency and its potential for low cost production and easy fabrication process as compared to traditional silicon based solar cells [2e4]. In DSSCs, the key component is a sensitizer, due to its function of light harvesting and electron injection capacity [5,6]. Ruthenium-based sensitizers (N3, N719 and black dye) are the most representative and most successful in DSSCs due to their long term stability and outstanding performances (PCE ¼ >10% at AM 1.5 condition) [7,8]. However, these dyes are inconvenient for commercial applications as they are very expensive, challenging synthesis, tedious purifi- cation, lower molar extinction coefficient and environmental is- sues. On the other hand, organic dyes (metal-free) are gradually attracting researchers attention due to the multiple advantages of relatively lower cost, high molar extinction coefficient, easy syn- thesis and excellent flexibility in structure modification, easily tunable functionalities and the photophysical as well as photo- chemical properties of dyes [9e12]. In the recent past, donorepeacceptor (D-p-A) structures based on organic sensitizers were constructed to achieve efficient solar energy harvesting. For efficient dye materials, different donor moieties such as carbazole, thiopene substituted carbazole, triphenylamine and phenothiazine are incorporated with cyanoacrylic acid as acceptor/anchoring group (Fig. 1). Because these donors have good electron donating ability and cyanoacrylic acid has efficient electron injection ability, it is believed that both can improve the overall performance of the dye molecules. Spacer/pelinker in between the donor and acceptor also plays a crucial role for the superior performance of the cell [13e16]. * Corresponding author. ** Corresponding author. E-mail addresses: soni_b21@yahoo.co.in (S.S. Soni), pki@iitg.ernet.in (P.K. Iyer). Contents lists available at ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel http://dx.doi.org/10.1016/j.orgel.2016.10.024 1566-1199/© 2016 Elsevier B.V. All rights reserved. Organic Electronics 39 (2016) 371e379