Effects of adding cyanovinyl moiety on the photovoltaic DSSCs phosphonic acid based cells
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Effects of adding cyanovinyl moiety on the photovoltaic DSSCs phosphonic acid based cells Driss Fadili1 · Si Mohamed Bouzzine1,2 · Mohamed Hamidi1
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Donor–acceptor–π–acceptor (D–A–π–A) dyes represent a promising alternative to their ancestor pull–push D–π–A structures for use in dye-sensitized solar cell (DSSC) applications. D–A–π–A dyes exhibit a red-shift and notable photostability in comparison with D–π–A dyes. Nevertheless, the effects of the position of the cyano moiety in the terminal acceptor of monofunctionalized phosphonic acid on the charge transfer (CT) in DSSCs remain unclear. Density functional theory (DFT) and time-dependent DFT (TDDFT) are applied herein to study the effects of the insertion of an electron-withdrawing cyanovinyl moiety and the position of the cyanide moiety on the geometrical, photophysical, CT, and nonlinear optical properties and reorganization energy of the designed dyes. The calculations reveal that a position of the CN moiety in the cyanovinyl phosphonic acid close to the anchor (CCCN2) results in the narrowest energy gap, and highest extinction factor and red-shift compared with the other dyes as well as the highest polarizability and first hyperpolarizability. Keywords DSSC · D–A–π–A · DFT · TDDFT · NLO · Phosphonic acid
1 Introduction As solar energy is one of the most readily accessible and low-cost sources of renewable energy, numerous photovoltaic technologies have been developed to convert photons into electrical current. Most photovoltaic cells used today are based on silicon [1]. However, more efficient photovoltaic technologies based on organic dyes have emerged, including dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSC) [2]. Since their introduction by Grätzel and O’Regan in 1991 [3], DSSCs have attracted attention due to their semitransparent and flexible nature, the possibility of integrating them into building, and tunable color, representing a low-cost alternative to conventional, silicon solar cells [4]. Such devices have achieved a power conversion efficiency (PCE) of up to 13% [5]. The dyes used in DSSCs are * Mohamed Hamidi [email protected] 1
Equipe de Chimie‑Physique, Electrochimie et Environnement, Faculty of Science and Technology, University of Moulay Ismaïl, B.P. 509 Boutalamine, Errachidia, Morocco
Centre Régional des Métiers de l’Education et de la Formation, BP 8, Errachida, Morocco
2
metalorganic complexes [6] or metal-free dyes [7, 8]. Considering their low cost and ready synthesis, organic (metal free) dyes have huge potential in this regard. The mechanism underlying the operation of a DSSC involves four main steps: in the first step, the dye or dye–TiO2 complex absorbs the incident photon; in the second step, the sensitizer is excited from the ground to an excited state, where the electron is injected into the conduction band (CB) of TiO2; in the third step, the injected electrons are transported to the counterelectrode; in the four
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