Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Influence of reduced graphene oxide-TiO 2 composite nanofibers in organic indoline DN350 based dye sensitized solar cells Jyoti V. Patil a,b , Sawanta S. Mali b , Jasmin S. Shaikh c , Akhilesh P. Patil d , Pramod S. Patil c,d , Chang Kook Hong b, ⁎ a Optoelectronic Convergence Research Center, Chonnam National University, Gwangju, 61186, Republic of Korea b Polymer Energy Materials Laboratory, School of Advanced Chemical Engineering, Chonnam National University, Gwangju, 61186, Republic of Korea c Thin film materials laboratory, Department of Physics, Shivaji University, Kolhapur, 416-004, India d School of Nanoscience and Technology, Shivaji University, Kolhapur, 416-004, India ARTICLE INFO Keywords: Reduced graphene oxide TiO 2 nanofibers DN350 Indoline Dye based DSSC ABSTRACT In this study, the highly efficient organic indoline DN350 based dye sensitized solar cells (DSSCs) have been fabricated using reduced graphene oxide (rGO)-TiO 2 composite nanofibers (NFs) and tested its photovoltaic properties. The influence of the rGO on the morphology, structural properties of the TiO 2 NFs have been characterized by various techniques. Our photovoltaic results revealed that the modified rGO-TiO 2 composite NFs exhibited higher power conversion efficiency (PCE) in comparison with the pristine-TiO 2 NFs. The elec- trochemical analysis indicated that the GO content provides more active sites results in higher dye adsorption which consequently improves the DSSCs performance. Our optimized sample containing 4 mg-rGO-TiO 2 NFs exhibited the best performance with 4.43% PCE, which is higher than the pristine-TiO 2 NFs (3.83%). Overall, this study presents the rGO-TiO 2 composite NFs as a novel strategy for enhancing the efficiency of the organic indoline DN350 based DSSCs. 1. Introduction Nowadays, tremendous research work is going on graphene and its related composite nanomaterials in the rapidly growing materials sci- ence area because of its promising properties towards practical appli- cations. The graphene is playing a key role in the field of nanoscience and nanotechnology from photocatalysis to biomedical applications. The single layer of graphene sheet showed an excellent electronic properties obeying Dirac physics for the use of promising electronic material. This single layered graphene sheet has zero band gap energy similar to the superconductors. However, a semi-metallic properties comes from the multilayered graphene with overlapped band gaps. It is also noted that, if there are multi-layers or any defect then these gra- phene sheets show semi-metallic properties. Therefore, graphene has been considered in different potential applications including nanoe- lectronics [1,2], field-effect transistors [3], spintronics [4], tunneling devices [5], dye sensitized solar cells (DSSCs) [6–9], organic photo- voltaics (OPVs) [10], perovskite solar cells (PVSCs) [11], super- capacitor [12], batteries [13], nanophotonics [14], catalysis [15], gas sensors [16], electrochemical sensors [17], drug carriers [18] and DNA biosensors [19,20]. So far, the number of methods have been developed for the synthesis of graphene sheets such as chemical vapor deposition (CVD), chemical exfoliation, epitaxial growth on SiC, unzipping of carbon nanotubes, scotch tape, mechanochemical cleavage and other organic synthesis protocols [21–24]. However, high-yield purity of the graphene or reduced graphene oxide (rGO) is a challenging task. Hummer’s method is one of the most promising approach to synthesize graphene oxide (GO) [25] for better yield with purity. Therefore, the implementation of rGO in DSSCs opens new approaches. The DSSC device contains the working photoelectrode loaded with dye molecules, iodine redox based couple electrolyte and Pt coated fluorine doped tin oxide (FTO) coated glass substrate as catalytic counter electrodes. The operation of rGO-TiO 2 nanofibers (NFs) based DSSCs is same while here, the rGO-TiO 2 acts as an electron transporting material. As per as the nanocrystalline TiO 2 is a concern, it has been widely used as a most promising n-type wide band gap semiconducting materials for DSSCs application. However, still, it has low-electron mobility and the number of grain boundaries. Therefore, it is necessary to improve the conductivity of the TiO 2 by implementing positive do- pant. The electron mobility can be improved by suitable metal doping. Therefore, various metal dopants such as Mg [26], Sn [27], Nb [28], Ta [29], Al [30], Li [31], graphene [32] and Au [33] have been used as an https://doi.org/10.1016/j.synthmet.2019.116146 Received 11 April 2019; Received in revised form 19 July 2019; Accepted 12 August 2019 ⁎ Corresponding author. E-mail address: hongck@chonnam.ac.kr (C.K. Hong). Synthetic Metals 256 (2019) 116146 Available online 20 August 2019 0379-6779/ © 2019 Elsevier B.V. All rights reserved. T