Pyridomethene–BF₂ complex/phenothiazine hybrid sensitizer with high molar extinction coefficient for efficient, sensitized solar cells

Abstract

A series of new pyridomethene-BF2/phenothiazine-hybrid metal-free organic sensitizers K1-K8 containing different πspacers were synthesized and applied in dye-sensitized solar cells (DSSC). The introduction of the pyridomethene-BF2 complex unit to the phenothiazine chromophore displayed a high molar extinction coefficient in favor of light-harvesting. Quantum chemical calculations were performed by using the density functional theory (DFT) at the B3LYP/6-31G (d,p) level to investigate the structural properties and electron density distributions of these dyes. The effect of dyes K1-K8 on the performance of DSSC was investigated systematically with comparisons to the plane phenothiazine dyes R1 and R2. Upon co-adsorption with deoxycholic acid, the dye K3 with a thiophene unit between the phenothiazine and pyridomethene-BF2 units exhibited the best photovoltaic performance. The short-circuit current density (Jsc) was 15.43 mA cm -2 with an open-circuit voltage (Voc) 0.69 V and a fill factor (FF) 0.62, that corresponded to a power-conversion efficiency (η) 6.58% under AM 1.5G irradiation (100 mW．cm -2 ) condition. The n-hexyl chain attached to the thiophene in K4-K5 exhibitted an effect of improving the Voc value. The presence of the phenyl pyridomethene-BF2 moiety at the N(10) atom of phenothiazine in K6-K8 showed a good effect of reducing π-π aggregation. These results revealed the advantage of incorporating a pyridomethene-BF2 group in the dyes for high performance DSSC cells.

Tuning Thiophene‐Based Phenothiazines for Stable Photocatalytic Hydrogen Production

“…In the H 2 productiono ver2 0h,t he new thiophenebased sensitizers revealed improved stabilityafter longerirradiation times and enhanced performances, in terms of H 2 productionr ates and light-to-fuel efficiencies,a fter an initial activation period, which weref or the first time associated with enhanced stability under photocatalytic production of H 2 and the absence of critical dye degradation. [21][22][23][24][25][26][27] Triggered by recent studies on phenothiazine (PTZ) derivatives as DSSC sensitizers [28][29][30][31] and by their first uses as light harvesters in the photo-driven productiono fH 2 , [32][33][34] we decided to systematically investigate this promising class of dyes by designing as eries of organic sensitizers containing the PTZ core as ad onor scaffold in donor-p-acceptor molecules. [14] Metal-freeo rganic sensitizers have gained an increasing role in the scientific literature of H 2 production, [15][16][17] with record DSSC powerc onversione fficiencies (PCE) exceeding1 2%.…”

“…[18][19][20] These dyes carry important advantages over metal complexes, such as easier and cheaper synthesis and purification, larger structural variety, and wider tunability of optical and energetic properties,w hich are fundamental to optimize the corresponding solar devices. [21][22][23][24][25][26][27] Triggered by recent studies on phenothiazine (PTZ) derivatives as DSSC sensitizers [28][29][30][31] and by their first uses as light harvesters in the photo-driven productiono fH 2 , [32][33][34] we decided to systematically investigate this promising class of dyes by designing as eries of organic sensitizers containing the PTZ core as ad onor scaffold in donor-p-acceptor molecules. Interestingly, av ery recent report on ac lass of benzo[b]phenothiazines confirms the increasing relevance of dye-sensitized H 2 production using organic dyes and PTZ derivatives.…”

The Structure-property Relationships of D-π-A BODIPY Dyes for Dye-sensitized Solar Cells

“…Recently, Chow and coworkers reported a series of new pyridomethene‐BF 2 /phenothiazine‐hybrid metal‐free organic sensitizers K1−K8 containing different π‐spacers, which were applied in DSSCs (Scheme ) . The introduction of the pyridomethene‐BF 2 complex unit to the phenothiazine chromophore displayed a high molar extinction coefficient in favor of light‐harvesting.…”

“…For this reason, BODIPY dye sensitizers for DSSCs have attracted considerable attention in the last decade . Various BODIPY dyes for DSSCs have been designed and synthesized, including D‐A BODIPY dyes tested in DSSCs with liquid electrolytes10–24 or solid‐state DSSCs, BODIPY dyes used as electron donor in bulk heterojunction solar cells, and BODIPY unit(s) used as the light antennae of a dye . Among them, D‐A BODIPY dyes tested in liquid DSSCs have the best photovoltaic performance.…”

Structure–Property Relationship Study of Donor and Acceptor 2,6‐Disubstituted BODIPY Derivatives for High Performance Dye‐Sensitized Solar Cells

“…More recently, a couple of photosensitizers based on porphyrin‐BODIPY dyads were reported to have a PCE as high as 6.2 %, However, the BODIPY moiety here plays a role of auxiliary electron donor (not a 2,6‐disubstituted π‐conjugation system) to porphyrin and how much of its contribution to PCE is not clear. Similarly, a BODIPY moiety was used as an electron donor (not a 2,6‐disubstituted π‐conjugation system) in a series of D‐π‐A type photosensitizers, although the fabricated DSCs exhibit PCE as high as 6.6 % . Another recently reported BODIPY having 2‐cyanoacrylic acid directly appended (without an acceptor π‐spacer in between) and an acetylene linkage to diphenylamine donor.…”