Computational studies of the influence of auxiliary acceptors in the D-A'-π-A structure of organic dyes on the photovoltaic performance of dye solar cells.

CONTEXT: A series of five organic dyes (Mi, i = 1-5) of the D-A'-π-A structure were designed based on reference dye (Ref), and the influence of different auxiliary acceptors (A') on their efficiency in dye-sensitized solar cells (DSSC). METHODS: Was studied theoretically using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. In this context, the electronic structures, optical properties, and the parameters influencing the power conversion efficiency (PCE), such as light harvesting efficiency (LHE), electron injection driving force (∆Ginject.), and open circuit photo-voltage (VOC), have been evaluated and discussed. The modification of the auxiliary acceptor (A') in the D-A'-π-A structure of the designed organic dyes has the advantage of significantly decreasing the band gap, which leads to the broadening of the absorption band that is red-shifted and improves the photovoltaic characteristics compared to Ref. Theoretical results reveal that M1, and M5 can be used as excellent sensitizer candidates for DSSC applications.

A theoretical study on the role of the π-spacer in the thoughtful design of good light-absorbing dyes with phenothiazine for efficient dye-sensitized solar cells (DSSCs).

CONTEXT: In this work, we designed ten new organic phenothiazine dyes bridged by different πi-spacers (PTZ1-PTZ10) of D-π-A type based on the synthesized dye CC202-III for their efficacy in dye-sensitized solar cells (DSSC) applications. To learn how various π-spacers affect their performance in DSSCs, these isolated dyes and dye-cluster systems have had their geometries, electronic structures, absorption spectra, dipole moments, and molecular electrostatic potential examined and talked about. Additionally, a number of quantization parameters that affect power conversion efficiency (PCE), including light collection efficiency (LHE), reorganization energy (λtotal), vertical dipole moment (µnormal), strength electron injection driving force (ΔGinject), regeneration driving force (ΔGreg), excited state lifetime (τ), and open circuit voltage (VOC), were calculated in order to identify the organic dyes that would be best suited for DSSC applications. Calculated results revealed that the designed dyes PTZ3, PTZ4, PTZ5, and PTZ10 exhibit a lower energy gap among all dyes compared to the corresponding CC202-III. Additionally, PTZ3, PTZ4, PTZ5, PTZ7, PTZ8, PTZ9, and PTZ10 exhibit significant red-shifted absorption spectra compared to the other dyes with a larger oscillator strength, which improves the photocurrent density of the devices. The findings thus imply that bridge modification is a workable tactic to raise DSSC effectiveness. METHOD: We used density functional theory (DFT) and time-dependent DFT (TD-DFT) methods to study the electronic and photovoltaic properties of the dyes designed (PTZ1-PTZ10) to assess their effectiveness in DSSCs. DFT and TD-DFT simulations are theoretically used to deeply analyze key characteristics of all organic dyes that affect open-circuit voltage (VOC) and short-circuit current (JSC) to identify structure-property relationships.

Theoretical investigation by DFT and TDDFT the extension of π-conjugation of novel carbazole-based donor materials for bulk heterojunction organic solar cell applications.

In this study, we have proposed seven designed symmetrical compounds (C2-C8) having a D-π-A-π-D structure based on derivative carbazole as a donor by introducing various π-spacer groups into the reference compound C1-Ref having a D-A-D structure in order to understand the influence of different π-spacers on their efficiency in BHJ solar cells. Various parameters such as geometrical structures, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), nonlinear optical properties (NLO), optical properties, light-harvesting efficiency (LHE), reorganization energy, chemical reactivity indices, exciton binding energy (Eb), open-circuit voltage (VOC), and fill-factor (FF) have been investigated using the density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The results show that the extended π-conjugation of the designed compounds (C2-C8) produces a lower energy gap (Eg), a stronger and broader absorption spectrum, lower reorganization energies and exciton binding, and higher nonlinear optical properties compared to C1-Ref, indicating that these designed compounds are promising as electron donors in BHJ-OSCs. Additionally, the calculated Voc, FF, and LHE of all compounds showed that the C2, C3, C4, C5, and C7 compounds have the best performance in BHJ solar cells compared to the others. In particular, C4 and C5 are excellent candidates for the effective donor materials of BHJ solar cells due to their large Voc, FF, and LHE than the other compounds. This theoretical investigation is expected to provide new strategies to synthesize efficient donor materials for BHJ-OSCs.