Kambiz Hosseinpanahi Department of Biosystems Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad 9177948978, Iran e-mail: Hosseinpanahi.kambiz@stu.um.ac.ir Mohammad Hossein Abbaspour-Fard 1 Professor Department of Biosystems Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad 9177948978, Iran e-mail: abaspour@um.ac.ir Javad Feizy Assistant Professor Department of Food Chemistry, Research Institute of Food Science and Technology (RIFST), Mashhad 9177948978, Iran e-mail: feizy.j@gmail.com Mahmood Reza Golzarian Assistant Professor Department of Biosystems Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad 9177948978, Iran e-mail: mahmoodgolzarian@gmail.com Dye-Sensitized Solar Cell Using Saffron Petal Extract as a Novel Natural Sensitizer Natural dye extract of the saffron petal, purified by solid-phase extraction (SPE) tech- nique, has been studied as a novel sensitizing dye to fabricate TiO 2 nanoparticles-based dye-sensitized solar cells (DSSC). The extract was characterized using ultraviolet–visible (UV–Vis) and Fourier transform infrared (FTIR) spectroscopies to confirm the presence of anthocyanins in saffron petals. The typical current–voltage and the incident photon to current efficiency (IPCE) curves were also provided for the fabricated cell. The saffron petal extract exhibited an open-circuit voltage (Voc) of 0.397 V, short circuit current den- sity (Jsc) of 2.32 mA/cm 2 , fill factor (FF) of 0.71, and conversion efficiency of 0.66%, which are fairly good in comparison with the other similar natural dye-sensitized solar cells. These are mainly due to the improved charge transfer between the dye extract of saffron petal and the TiO 2 anode surface. Considering these results, it can be concluded that the use of saffron petal dye as a sensitizer in DSSC is a promising method for provid- ing clean energy from performance, environmental friendliness, and cost points of view. [DOI: 10.1115/1.4034908] Keywords: saffron petal, delphinidin, TiO 2 , nanoparticle, dye-sensitized, solar cell Introduction Dye-sensitized solar cells (DSSC) are energy devices invented for converting visible light into electricity, based on the sensitiza- tion of wide-band gap metal oxide semiconductors such as TiO 2 [1]. Since their appearance in the 1991 s [2], DSSCs have drawn much attention from the scientific community, due to the ease of fabrication, low cost, the ability to generate electricity in cloudy conditions, and also under artificial light. In addition, there is no drop in their efficiency at high temperatures and they are also environmentally friendly [3,4]. As shown in Fig. 1, a DSSC con- sists of a metal oxide semiconductor, sensitizing dyes adsorbed onto the metal oxide semiconductor as anode, an electrolyte, and a counter electrode [5]. The primary processes that occur in a DSSC can be summarized as follows [6]: (1) The dye, upon absorption of a photon (ht), excited from the ground state (S) to the excited state (S*). (2) The excited electrons are injected into the conduction band of the TiO 2 electrode, resulting in the oxidation of the pho- tosensitizer. S þ ht ! S  (1) S  ! S þ þ e  ðTiO 2 Þ (2) (3) The injected electrons in the conduction band of TiO 2 are subsequently transported between TiO 2 nanoparticles with diffusion toward the back contact (TCO) and consequently reach the counter electrode through the external load and circuit. The oxidized photosensitizer (S þ ) accepts electrons from the I  ion redox mediator, regenerating the ground state (S), and I  is oxidized to the oxidized state, I  3 S þ þ e  ! S (3) (4) The oxidized redox mediator, I  3 , diffuses toward the coun- ter electrode and is reduced to I  ions. I  3 þ 2e  ! 3I  (4) Fig. 1 Schematic performance of a dye-sensitized solar cells reaction 1 Corresponding author. Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING:INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received April 16, 2016; final manuscript received September 18, 2016; published online November 29, 2016. Assoc. Editor: Wojciech Lipinski. Journal of Solar Energy Engineering APRIL 2017, Vol. 139 / 021009-1 Copyright V C 2017 by ASME Downloaded From: http://solarenergyengineering.asmedigitalcollection.asme.org/ on 12/03/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use