Synthesis of 2-amino-4-(4-(methylamino)phenyl)-6- phenylnicotinonitrile as a new additive for the passivation of the TiO 2 surface and retarding recombination in dye-sensitized solar cells Mohammad Mazloum-Ardakani * , Rezvan Arazi, Mahnoosh Haghshenas, Fatemeh Tamaddon, Masoumeh Alizadeh Department of Chemistry, Faculty of Science, Yazd University, Yazd 89195-741, Islamic Republic of Iran article info Article history: Received 28 October 2017 Received in revised form 1 January 2018 Accepted 3 February 2018 Available online 6 February 2018 Keywords: Dye-sensitized solar cells Electrolyte Additive Nicotinonitrile derivative Nanocrystalline TiO 2 semiconductor abstract In this research, we synthesized a phenylnicotinonitrile derivative as a new type of additives and studied its effect on the performance of dye-sensitized solar cells by UVeVis spectroscopy, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). In comparision with a blank electrolyte (0.35 M lithium iodide, 0.035 M iodine and 0.01 M guanidium thiocyanate in a much less leakage and volatile solvent such as propylene carbonate, PC-liquid), addition of 0.5 M phe- nylnicotinonitrile derivative caused an increase in the open-circuit potential (V oc ) of 209 mV but a decrease in the short current density (J sc ) of 3.36 mA/cm 2 . The increase could be attributed to the negative shift of the conduction bond of TiO 2 semiconductor potential (V oc , ~34% of the voltage increase) and to the increase of the photo-conversion efficiency (PCE, ~21% of the efficiency increase). The decrease in J sc was because of the reduction of dye regeneration and the catalytic activity of the photocathode in electrolyte regeneration. It was shown that the fabricated dye-sensitized solar cells (DSSCs)-based different electrolytes displayed the relative standard deviation (RSD) range of 3.24%e4.36% for six re- petitive measurements (n ¼ 6). © 2018 Elsevier Ltd. All rights reserved. 1. Introduction As an alternative to conventional silicon-based solar cells, DSSCs have raised great research interests due to their low manufacturing cost and environmentally friendly character [1e 7]. Dye-sensitized solar cells produce electricity through electron transfer. Light passes through a conductive glass electrode. In these cells, photons are absorbed by the surface-anchored dye by excitation of electrons from a HOMO level to a LUMO level. The excited electrons jump to a titanium dioxide layer and diffuse across this layer. The electrons move through a semiconductor to a current collector and an external circuit. Every dye molecule, having lost an electron to the titanium dioxide, is now oxidized, which means it has one fewer electron than before. The dye is then regenerated by a redox mediator in the pores, which ensures that the oxidized dye species are continuously regenerated and that the process is cyclic [1]. When the original lost electron reaches the counter electrode, it gives the electron back to the electrolyte to complete the cycle and generate a photocurrent. There are different strategies to optimize this dynamic process [2e4]. One of them is addition of organic molecules, as various additives, to the electrolyte to shift the con- duction bond (CB) of the semiconductor. Additives play an impor- tant role to improve the photoelectrochemical performance of DSSCs. Most additives are understood at a fairly phenomenological level, and their effects are often attributed to the modification of redox couple potentials, band shifts of semiconducting materials, effects of surface blocking, or surface dye organization. The position of the CB in the TiO 2 depends strongly on the dipolar molecule adsorption and surface charges [5]. In the electrolytes, these addi- tives are adsorbed onto the semiconductor surface, thus, affecting the CB in the TiO 2 dramatically accompanied by the effective changes in the photocurrent and the photovoltage. Therefore, introduction of additives into liquid electrolytes has been an effective strategy to improve DSSCs characterization. Nitrogen- containing heterocyclic and Lewis base compounds, such as pyri- dine derivatives, are one of the most frequently used type of ad- ditives in DSSCs, which mainly enhance the open-circuit voltage * Corresponding author. E-mail address: mazloum@yazd.ac.ir (M. Mazloum-Ardakani). Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta https://doi.org/10.1016/j.electacta.2018.02.011 0013-4686/© 2018 Elsevier Ltd. All rights reserved. Electrochimica Acta 266 (2018) 452e459