Comparative Studies on the Structure–Performance Relationships of Phenothiazine-Based Organic Dyes for Dye-Sensitized Solar Cells

Abstract

A D–A−π–A dye ( PTZ-5 ) has been synthesized by introducing a benzothiadiazole (BTD) unit as an auxiliary acceptor in a phenothiazine-based D−π–A dye( PTZ-3 ) to broaden its spectral response range and improve the device performance. Photophysical properties indicate that the inclusion of BTD in the PTZ-5 effectively red-shifted the absorption spectra by reducing the E gap . However, the device measurements show that the open-circuit voltage ( V oc ) of PTZ-5 cell (640 mV) is obviously lower than that of the PTZ-3 cell (710 mV). This results in a poor photoelectric conversion efficiency (PCE) (4.43%) compared to that of PTZ-3 cell (5.53%). Through further comparative analysis, we found that the introduction of BTD increases the dihedral angle between the D and A unit, which can reduce the efficiency of intramolecular charge transfer (ICT), lead to a less q CT and lower molar extinction coefficient of PTZ-5 . In addition, the ESI test found that the lifetime of the electrons in the PTZ-5 cell is shorter. These are the main factors for the above unexpected result of PCE. Our studies bring new insights into the development of phenothiazine-based highly efficient dye-sensitized solar cells (DSSCs).

Synthesis of 2,5-bis(9H-fluoren-9-ylidene)-2,5-dihydrothiophene derivatives and a systematic study of the substituent effect

“…The reduction of the molar extinction coefficient for B2–B4 and B7–B9 might also be caused by the increase of dihedral angles, which hinder the electron flow along the quinoidal π-conjugation system. 24…”

New 3-Ethynylaryl Coumarin-Based Dyes for DSSC Applications: Synthesis, Spectroscopic Properties, and Theoretical Calculations

“…Although the original ruthenium(II)-polypyridyl chromophores used in DSSCs, such as N3 [6] and N719 [7], have mostly remained as gold standard dyes due to their large conversion efficiencies [8], their only moderate extinction coefficients and the use of a rare and expensive noble metal has led to the extensive search for highly efficient metal-free dyes. These metal-free dyes offer, in addition to the lower cost of production, easier and greater synthetic versatility and tunable optical and electrochemical properties through structural modification, as demonstrated by the extremely wide array of compounds explored over the years [9][10][11]. Despite being mostly overshadowed by their inorganic counterparts, in recent years comparable or even superior performances have been achieved by metalfree chromophores, such as bulky indoline-quinoxaline dyes (10.65%) [12], tetrathioacene dyes (10.1%) [13] and more elaborate polycyclic aromatic push-pull dyes (12.6%) [14], all employing a Co(II/III) complex as redox shuttle.…”

A Molecular Engineering Strategy of Phenylamine-Based Zinc-Porphyrin Dyes for Dye-Sensitized Solar Cells: Synthesis, Characteristics, and Structure–Performance Relationships

“…So far, many electron-rich D units with various moieties such as phenylamine, − phenothiazine, ,− phenoxazine, , and carbazole have been developed. In this respect, Xie and co-workers have synthesized a series of porphyrin sensitizers containing triphenylamine and phenothiazine as the electron-donating unit, which show excellent performance. , Meanwhile, a series of studies demonstrated that the flexible introduction of alkoxy or alkyl chains into D units, the β-position, and the acceptor unit was conducive to anti-aggregation and thus improved the short-circuit current densities ( J sc ) and PCE. ,− Furthermore, the electron-deficient moieties, such as benzothiadiazole (BTD), , benzotriazole, and 3,4-ethylenedioxythienylene have also been studied in developing porphyrin sensitizers. Among these auxiliary acceptors, BTD has been proven to be an excellent construction …”

“…7,8 Meanwhile, a series of studies demonstrated that the flexible introduction of alkoxy or alkyl chains into D units, the β-position, and the acceptor unit was conducive to anti-aggregation and thus improved the short-circuit current densities (J sc ) and PCE. 17,27−31 Furthermore, the electron-deficient moieties, such as benzothiadiazole (BTD), 35,36 benzotriazole, 37 and 3,4-ethylenedioxythienylene 38 have also been studied in developing porphyrin sensitizers. Among these auxiliary acceptors, BTD has been proven to be an excellent construction.…”