Charge Transfer as Bridging Correlator for DSSC Efficiency and NLO Property

Abstract

The efficacy of dipyridyl and diphenylamine sensitizers in dyesensitized solar cells (DSSCs) is linked to trends in DFT-based charge transfer and non-linear optical (NLO) properties. We chose DFT and Time-dependent-DFT methods. The planarity is improved by replacing the phenyl ring at the donor site with a thiophene ring. Similarly, cyanoacetic acid acceptor improves planarity over rhodamine-3-acetic acid acceptor. In all cases in HOMO, the electron density is located at the donor and some part of the spacer, and in LUMO, it is shifted to the acceptor. Bond length alternation, bond order alternation, quinoid character, effective charge transferred distance, effective charge transferred, chemical potential, electrophilicity index, and electron correlation descriptors showed direct relation, while hardness and hyperhardness showed an inverse relation with NLO properties. We observed higher β 0 and γ for thiophenebased sensitizers ranging from 248.81 × 10 À 30 to 440.92 × 10 À 30 esu and 777.82 × 10 À 36 to 1442.69 × 10 À 36 esu, respectively. Likewise, more negative values of ΔGinject (À 0.630 to À 0.752 eV), a smaller value of ΔGreg (0.662 to 0.790 eV), and higher LHE (0.959 to 0.976) are observed for thiophene-based sensitizers. Also, thiophene-based sensitizers showed shorter TiÀ O bond lengths than their phenyl-based sensitizers. Photovoltaic parameters are directly related to DSSC efficiency and NLO properties.

A promising small-sized near-infrared absorbing zwitterionic dye for DSSC and NLO applications: DFT and TD-DFT approaches

“…In the MEP plot, the increase in potential energy is understood through the variation in color change from blue to red, where the blue region signifies the electrophilic and the red area indicates the nucleophilic center. 69,71,72 The generated MEP plots of the ZIDM, ZIMCA, and ZIDCA in gas and DCM are shown in Fig. 3b.…”

“…The following equation can be used for calculating the J SC 66,68 where LHE is the light-harvesting efficiency at the highest absorption maxima, Φ inj is the electron injection efficiency, η coll is the charge collection efficiency. When η coll coll in a system is considered constant, the LHE ( λ ) is calculated as 66–69 LHE = 1–10 − f where f denotes the oscillator strength of dye at a particular wavelength. In contrast, Φ inj is associated with the driving force ( G inject ) of electrons injected into the semiconductor from the dye's excited state, as discussed below 66–69 Φ inj ∝ (−Δ G inject )wherewhere is the dyes’ excited state oxidation potential and E CB is the semiconductor (TiO 2 ) conduction band ( E CB (TiO 2 ) = −4.0 eV).…”

“…When η coll coll in a system is considered constant, the LHE ( λ ) is calculated as 66–69 LHE = 1–10 − f where f denotes the oscillator strength of dye at a particular wavelength. In contrast, Φ inj is associated with the driving force ( G inject ) of electrons injected into the semiconductor from the dye's excited state, as discussed below 66–69 Φ inj ∝ (−Δ G inject )wherewhere is the dyes’ excited state oxidation potential and E CB is the semiconductor (TiO 2 ) conduction band ( E CB (TiO 2 ) = −4.0 eV). 66–69 of a dye can be calculated through the equation given below 66–69 where E dye ox is the dye's ground state oxidation potential energy and E vert is the vertical excitation energy associated with λ vert .…”

“…In contrast, Φ inj is associated with the driving force ( G inject ) of electrons injected into the semiconductor from the dye's excited state, as discussed below 66–69 Φ inj ∝ (−Δ G inject )wherewhere is the dyes’ excited state oxidation potential and E CB is the semiconductor (TiO 2 ) conduction band ( E CB (TiO 2 ) = −4.0 eV). 66–69 of a dye can be calculated through the equation given below 66–69 where E dye ox is the dye's ground state oxidation potential energy and E vert is the vertical excitation energy associated with λ vert . E dye ox is defined as the negative of the highest occupied molecular orbital energy ( E HOMO ).…”

“…A sensitizer's effectiveness in DSSC is impacted by the driving force of regeneration (Δ G reg ) energy since it directly affects the short circuit current ( J SC ). The following equation can be used to determine Δ G reg 69 Δ G reg = E redox − E dye ox where E redox is the electrolyte's redox potential i.e. , I − / I 3 − = −4.80 eV.…”