Contents lists available at ScienceDirect Optik journal homepage: www.elsevier.com/locate/ijleo Original research article Lily (Iris Persica) pigments as new sensitizer and TiO 2 nanofibers as photoanode electrode in dye sensitized solar cells Shadman Mansouri a , Mohammad Hossein Abbaspour-Fard a, *, Azadeh Meshkini b a Department of Biosystems Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, P.O. Box 91775-1163, Mashhad, Iran b Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, P.O. Box 91775-1436, Mashhad, Iran ARTICLE INFO Keywords: Dye sensitized solar cell (DSSC) Wild lily dyes TiO 2 nanofibers Electrospinning ABSTRACT In this study, lily (Iris Persica) dyes as sensitizer were examined by UV–vis and FTIR analyses. Corresponding results showed that lily pigments effectively absorb incident light. This was mainly due to the presence of functional groups such as C]O and OeH in the pigment structure appeared on the FTIR analysis. This shows the appropriateness of lily pigment as sensitizer. On the other hand, anatase TiO 2 nanofibers with different diameters were synthesized by Electrospinning method, using Titanium isopropoxide (TIPP) and polyvinylpyrrolidone (PVP) solution. The Electrospinning feed rate was altered from 0.1 to 0.5 mL/h to control the diameter of the TiO 2 nanofibers. Other effective parameters including voltage, needle tip distance to collector and speed of collector were 25 kV, 15 cm and 500 rpm, respectively and were kept constant during synthesizing of nanofibers. The Synthesized nanofibers were analyzed and characterized by means of SEM, FESEM, XRD and TEM techniques. The FESEM and XRD analyses indicated that the nanofiber's diameter and crystallinity increase with increase in feed rate. The fabricated DSSC with 430 nm TiO 2 nanofibers (obtained from flow rate of 0.3 mL/h) provided 1.72 % energy conversion efficiency (ղ), 50.78 % conversion efficiency of photon to electron (IPCE), short-circuit current density (J SC ) of 2.716 mA/cm 2 and open circuit voltage (V OC ) of 0.738 V. The efficiency of the developed DSSCs, in comparison with the previously fabricated similar cells, were found higher, due to more effective absorption of light by the dyes and ad- sorption of pigment by nanofibers. 1. Introduction Dye sensitized solar cells (DSSCs) are cost effective type of solar cells with wonderful advantages [1,2] that makes them as top substitute to conventional solar cells. To commercialize the DSSCs, investigations are on the go [e.g. 3]. The dye sensitized solar cells were primarily introduced by Grätzel and O’Regan in 1990 [2] followed by 7 % efficiency development in 1991 [4,5]. Since then efficiency was gradually improved to 11 % [6]. Mathew et al. enhanced power conversion efficiency of DSSC cells up to 13 % [7]. Efficiencies of natural dyes were improved to a maximum of 14.7 % [8]. However, to overtake silicon solar cells, efficiency should be greater than 20 % [9]. The structure of DSSC solar cells comprises three main components (Fig. 1)[4,7,10]. The DSSC working cycle can be found elsewhere [7,11]. The performance of DSSCs is affected by photoanode [12] and dye sensitizers. In the meantime, researchers found natural dyes interesting [3,13]. In comparison with synthetic or artificial dyes, natural https://doi.org/10.1016/j.ijleo.2019.163710 Received 28 July 2019; Received in revised form 21 October 2019; Accepted 5 November 2019 ⁎ Corresponding author at: Department of Biosystems Engineering, Faculty of Agriculture, Ferdowsi University of Mashhad, University campus, Azadi Square, P.O. Box 91775-1163, Mashhad, Iran. E-mail addresses: sh_ma591@mail.um.ac.ir (S. Mansouri), abaspur@um.ac.ir (M.H. Abbaspour-Fard), a.meshkini@um.ac.ir (A. Meshkini). Optik - International Journal for Light and Electron Optics 202 (2020) 163710 0030-4026/ © 2019 Elsevier GmbH. All rights reserved. T