Design and theoretical study of phenothiazine-based low bandgap dye derivatives as sensitizers in molecular photovoltaics

Abstract

Modulation of metal free organic (MFO) molecules become imperative to researchers to obtain low-cost sensitizer for dye sensitized solar cells (DSSCs) purposes. A series of metal free phenothiazine-based (PTZ) organic dyes are designed and optimized as sensitizers for DSSCs application. Their electronic and optical properties were probed using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) approaches. Effects of additional donor unit, π-conjugation bridges, and benzothiadiazole (BTDA) were investigated. Introducing BTDA in the acceptor unit leads to the tailoring of the energy band gap and promotion of charge transfer within donor and anchor groups with increased effective parameters in DSSC efficiency. The addition of diphenylamine, triphenylamine, or hexyloxyphenyl to the PTZ unit increased electron delocalization and enhanced intramolecular charge transfer. Changing π-spacer from phenyl to thiophene has a great effect on the electronic properties and absorption spectra of the dyes. The relationship between light harvesting efficiency (LHE) and chemical hardness (ƞ) shows that structural design that consists of BTDA and thiophene as π-spacer tends most towards excellent performance as dye sensitizers in DSSCs.

Tuning optical properties of triphenylamine‐pyrrole by alkyl‐substituted thiobarbituric acid for dye‐sensitized solar cell

“…[13][14][15] The efficiency of the DSSCs is affected by the electron donating ability, the spacer linearity, and the acceptor end group. Among others, carbazole derivatives, 16,17 coumarin, 13 phenothiazine, [18][19][20] and triphenylamine 21,22 have been widely used as electron donors, which was due to electron donating ability, easy functionalization, high mobility, and wide-range solar light absorption. To design DSSCs with high PCE, the absorbed sunlight by the photosensitizers is injected to the conduction band of the semiconductor through efficient acceptor end group.…”

Electronic and optical properties’ tuning of phenoxazine-based D-A2-π-A1 organic dyes for dye-sensitized solar cells. DFT/TDDFT investigations

“…Thus, E g can be expressed as in Eq. (1) [ 58 , 60 ]. E g = E LUMO −E HOMO where E LUMO and E HOMO are the energies associated with the lowest unoccupied molecular orbital and the highest occupied molecular orbital respectively.…”

“…The conductor like polarizable continuum model (C-PCM) in the gas phase was the solvation model employed. Since the improvement of absorbed dyes could probably result in good LHE [ 52 , 63 ], thus absorption in the visible and near-ultraviolet (UV) region of the spectrum is crucial for light-to-current conversion [ 13 , 60 ]. Also, low E g is essential to produce higher λ max and increase the efficiency of DSSCs.…”

“…High LHE is suitable to increase the photocurrent response through intramolecular charge transfer [ 60 ]. The LHE values of the simulated dyes are 0.70, 0.68, 0.65, 0.68, 0.70, 0.68, 0.65 and 0.01 (P1 to P8 respectively) as reported in Table 5 .…”

Comparison of semi‐empirical and density functional approaches for the colour and constitution of anthraquinone dyes using X‐ray structure

“…The effective design of organic dyes is one area where experimental synthesis and theoretical prediction can effectively interact. [1][2][3] Molecular orbital (MO) calculation is therefore an essential tool for the research and development of functional dyes. The main purpose of MO calculation in functional dye research is to examine optimised molecular structure and to predict and/or interpret the excited states with respect to absorption properties based on the optimised molecular structure.…”