Theoretical Study of Sensitizer Candidates for Dye-Sensitized Solar Cells: Peripheral Substituted Dizinc Pyrazinoporphyrazine–Phthalocyanine Complexes

Abstract

We have carried out a theoretical study of the geometrical and electronic structures of a family of planar dimers constituted by zinc(II) pyrazinoporphyrazine and zinc(II) phthalocyanine with peripheral electron-donating and electron-withdrawing substituents R [where R = -OH (1), -C(CH(3))(3) (2), -CH(3) (3), -C(6)H(5) (4), -H (5), -CO(2)H (7), -NO(2) (7), and -PO(3)H(2) (8)]. The complexes are connected by varying the bridge (B) ligand, where, in 1-9, B is -CH= and, in 10-12, B is -N=, -O-, and -S-, respectively. The -CO(2)H group was included in complexes identified as 9-12. This was done because of the known properties of this group in acting as an anchor to adsorb a dye onto a semiconductor oxide. The aim of this work was to provide a useful theoretical basis for the design and screening of new potential dye candidates to be used in these devices, based on the properties of the dyes suitable for their good performance in solar cells, such as frontier molecular orbital spatial distributions; charge-separated states in the electronic transitions in the visible region of the spectrum; and importantly, the energy diagram of the frontier MOs of these dyes and the conduction band (CB) of the semiconductor, where the LUMO energy levels that are above of the CB suggest which dyes are capable of electron injection into TiO(2). In this sense, it is expected that complexes 1-5 and 9-12 should be very promising dyes to act as sensitizers. Finally, a linear correlation was found between the HOMO and LUMO energies of all of the systems and the Hammett constants, where these molecular orbitals become more stable when R is more electron-withdrawing.

Study of the Molecular Properties of Mono- and Binuclear Metal s-Indacenyl Complexes with Ir, Rh, and Re: A Theoretical Approach

“…The estimated chemical potential ( ), chemical hardness ( ), and electrophilicity ( ) have been analyzed [25][26][27][28][29]. This set of values is reported in Table 3.…”

“…is related with its electronegativity as − and is associated with the feasibility of a system to exchange electron density with the environment at the ground state [25][26][27][28][29].…”

“…In numerical applications, these reactivity indexes are calculated following approximations using Koopmans' theory and finite differences leading to (3). Here, I and A correspond to the ionization energy and electron affinity, while ( ) and ( ) correspond to the orbital energies of the HOMO and LUMO, respectively [25][26][27][28]:…”

Interaction of YD2 and TiO2 in dye-sensitized solar cells (DSSCs): a density functional theory study

“…This is a fundamental influence on the geometric structure of the adsorbed dye state and the electronic coupling with the Ti(3d) conduction band. Over the past 5 years, a number of theoretical studies of solar cells utilizing ruthenium complexes that were performed at the quantum chemical (density functional theory) level and the molecular dynamics level have been published [18][19][20][33][34][35][36][37][38][39]. Those studies modeled the interaction of the ruthenium sensitizer with the (101) plane of (anatase) TiO 2 or a nanocluster of TiO 2 .…”

“…Thus, we performed a theoretical study to find out which anchor groups improve the conjugation with the macrocycle rings. The model systems considered in the calculations consisted of a dye attached to a TiO 2 cluster representing the TiO 2 surface [34][35][36][37][38][39]. Theoretical models including optimized molecular structures were used to identify and characterize suitable light-capturing molecules.…”