The influence of noncovalent interactions in metal‐free organic dye molecules to augment the efficiency of dye sensitized solar cells: A computational study

Abstract

The efficiency of dye sensitized solar cells (DSSCs) can be enhanced with achieving better planarity of metal‐free organic dye molecules and thinning of their aggregation on the semiconductor surface. We report that the subtle noncovalent N…S interaction between the substituted phosphazene group and thiophene spacer unit in dye molecule which induces the desired planarity and avoid aggregation of such molecules on the TiO2 surface using DFT calculations. DFT results show that phosphazene group increases the maximum absorption wavelength (λmax), driving force for electrons injection (ΔGinjection), singlet excited state lifetime (τ), dipole moments (μnormal), and number of electrons transferred from dye to TiO2 surface (Δq), which are known to augment the efficiency of DSSCs. Further, the lower ΔGregeneration value of phosphazene containing dyes (e.g., –.37 eV, dye 2) than the reported dyes (e.g., –.81 eV, dye 1) indicate the faster electron injection rate from the former dye to the semiconductor TiO2. The role of phosphazene group to prevent the aggregation of dye molecules on the TiO2 anatase surface was also examined with GGA‐PBE/DNP level of theory. The calculated results suggest that the dye molecules on 1‐(TiO2)38 and 2‐(TiO2)38 anatase clusters avoids the aggregation due to the steric congestion induced by phosphazene group. This work reports to accomplish dual properties with subtle noncovalent interactions in dye molecules to augment the efficiency in DSSCs.

A DFT study to probe homo-conjugated norbornylogous bridged spacers in dye-sensitized solar cells: an approach to suppressing agglomeration of dye molecules

“…The m normal is the dipole moment of the dye molecules which is perpendicular to the surface of the semiconductor and g is the concentration of the dye on the semiconductor surface. 10 The DFT functional Coulomb-attenuating Becke's threeparameter hybrid functional with the correlation formula of Lee, Yang, and Parr (CAM-B3LYP) provides useful accuracy for long-range orbital-orbital exchange interaction. This function is widely applicable for the polarizability of long-chain, excitation to Rydberg states and charge-transfer excitations.…”

“…41 For this advancement in the functional CAM-B3LYP is popularly used for DSSC. 10,40 The geometry optimizations were performed for dyes 1-6 with TiO 2 using CAM-B3LYP DFT functional in this study. All systems were fully optimized with the 6-31G(d) basis set for the C, H, O, N atoms and effective core potential (ECP) LANL2DZ and its associated basis set for the Ti atom.…”

“…The studied dye molecules were compared with a calculated ref-1 system, which possesses p-conjugated thiophene spacers at the same level of theory. 10 The donor molecule (3,9-dimethyl-9H-carbazole) used in ref-1 is a better donor in comparison to the N,N dimethylamine used in this study. The donor molecule (3,9-dimethyl-9H-carbazole) was synthetically prepared and used as a donor in several DSSCs.…”

“…A smaller gap in the position of HOMO and LUMO energy levels facilitates the electron injection and dye regeneration resulting in high power conversion efficiency (PCE). 10 A strong absorption band that could cover practically all visible and near-infrared light region to maximize the light-harvesting efficiency (LHE) and a good intramolecular charge transfer (ICT) is required to enhance the efficiency of the dye-sensitized solar cell. 11 The donor group attached to the dyes play a major role in the performance of DSSC.…”

Role of donor‐acceptor functional groups in N3P3 cyclic‐triphosphazene backbone. Unraveling bonding characteristics from natural orbitals within an extended transition state‐natural orbital for the chemical valence scheme

“…Even though cyclic-phosphazenes are of interest for both computational and experimental chemists, theoretical studies are scarce. [40][41][42][43][44][45][46] Due to the this fact, the aromatic response of some cyclic-triphophazenes was assessed through Nucleus Independent Chemical Shifts, and the electronic structure was analyzed by means of the Natural Bond Orbitals among others. [40] The assessment of the aromaticity of heterocyclicphosphazenes describes them as somewhat aromatics.…”