Influence of spatial arrangements of p-spacer and acceptor of phenothiazine based dyes on the performance of dye-sensitized solar cells Zafar Iqbal a,b , Wu-Qiang Wu c , Hai Zhang a , Lijun Han a , Xiaoming Fang a , Lingyun Wang a , Dai-Bin Kuang c,⇑ , Herbert Meier d , Derong Cao a,⇑ a School of Chemistry and Chemical Engineering, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510641, China b PCSIR Laboratories Complex, Feroze pur Road, Lahore 54000, Pakistan c MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, KLGHEI of Environment and Energy Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, China d Institute of Organic Chemistry, University of Mainz, Mainz 55099, Germany article info Article history: Received 7 May 2013 Received in revised form 9 July 2013 Accepted 10 July 2013 Available online 25 July 2013 Keywords: Organic dye Double acceptor Dye-sensitized solar cells Phenothiazine p-Extension Spatial arrangement abstract Three phenothiazine based organic dyes PTA, PDTA and PTDA with D–p–A, p–D–p–A and A–p–D–p–A frameworks were designed and synthesized for the dye sensitized solar cells (DSSCs). Phenothiazine with octyloxyphenyl moiety acts as donor while thiophene and cyanoacetic acid units act as a p-spacer and an acceptor, respectively. The effects of the molecular structures of the dyes on the performance of the DSSCs were investigated sys- tematically along with their photophysical and photoelectrochemical properties. The dye PTDA with A–p–D–p–A framework exhibited a better light harvesting capacity and an effective electron extraction pathway from the electron donor to the TiO 2 surface, leading to an efficiency of 6.82% under 100 mW cm À2 light illumination, while the dyes PTA and PDTA with D–p–A and p–D–p–A frameworks delivered efficiencies of 6.34% and 5.12%, respectively. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Substantial consumption of fossil fuel has been generat- ing a huge quantity of toxic gases, which leads to serious environmental issues. Current energy resources are deplet- ing rapidly, therefore searching for new clean and sustain- able energy resources as a substitute for the traditional fossil fuel is an urgent need [1]. Among renewable energy resources, the solar energy is one of the simplest and most obvious choice because it has largest potential to cater for the future global need without appreciable greenhouse ef- fect [2]. Among various kinds of emerging photovoltaic technol- ogies, dye-sensitized solar cells (DSSCs) have attracted a great deal of interests since 1991 [3]. DSSCs are being ac- cepted as a novel substitute to the conventional and expen- sive silicon based solar cells due to its low material cost, facile methods of fabrication and reasonably good power conversion efficiency [4–6]. Furthermore, DSSCs have been proved to be better in diffused light and at moderate temperature (up to 50 °C) [7,8]. DSSC is a rapidly growing technology due to several advantages, such as cheap and environment friendly materials, flexible and facile synthe- sis. It also has largest potential for mass production. Metal complexes based on ruthenium and zinc have been extensively studied for DSSCs and high efficiencies over 10–11% [9,10] and 12% [6] have been obtained. Ruthenium is a rare and expensive metal and its dyes have relatively low molar extinction coefficients. Furthermore, 1566-1199/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.orgel.2013.07.007 ⇑ Corresponding authors. Tel./fax: +86 20 87110245 (D. Cao), tel.: +86 20 84113015 (D.-B. Kuang). E-mail addresses: kuangdb@mail.sysu.edu.cn (D.-B. Kuang), drcao@scut.edu.cn (D. Cao). Organic Electronics 14 (2013) 2662–2672 Contents lists available at ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel