Exploratory synthesis and photovoltaic performance comparison of D–π–A structured Zn-porphyrins for dye-sensitized solar cells

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>The design and synthesis of D–π–A structured Zn(II)–porphyrin sensitizers with extended π-conjugation, coded as <B>SGT-012, SGT-016, SGT-052</B> and <B>SGT-053</B>, were explored. The key schematic concept for the molecular design and synthesis of porphyrin sensitizers, with the target of modulation of donor groups by embedding an electron donor into the skeleton of two typical D‐π‐A porphyrin models, such as D–porphyrin-A sensitizers (<B>SGT-012</B> and <B>SGT-016</B>) and D-triple bond-porphyrin-triple bond-<B>BTD</B>-acceptor sensitizers (<B>SGT-052</B> and <B>SGT-053</B>), was proposed investigate the influence of the donor ability and the bulk of donor groups on the photophysical properties and cell performance of dye-sensitized solar cells (DSSCs). Also, based on the photophysical properties and cell performances, the co-sensitisation strategy was conducted to further enhance the cell performances. <B>SGT-012</B> and <B>SGT-052</B> porphyrins, containing a strong donor unit, exhibited similar S-band absorption and a slightly red-shifted Q-band absorption compared to <B>SGT-016</B> and <B>SGT-053</B> porphyrins containing a weak bulky donor unit, respectively. To further extend the π-conjugation and absorption to a longer wavelength range, the triple bond at two <I>meso</I>-positions of the porphyrin core and a benzothiadiazole (<B>BTD</B>) strong electron acceptor was introduced to yield <B>SGT-052</B> and <B>SGT-053</B>, resulting in a red-shift and broad visible region absorption ability. It was indicated that these modifications lead to the formation of a stronger intramolecular charge transfer complex, which is favourable for harvesting sunlight, than those of <B>SGT-012</B> and <B>SGT-016</B> porphyrins. To prevent undesirably reduced <I>V</I> <SUB>oc</SUB> caused by charge recombination processes and dye aggregation from porphyrin-sensitized solar cells, <B>HC-Al</B> of co-adsorbent was adopted to fabricate <B>SGT-052-</B> and <B>SGT-053</B>-based solar cells. The DSSCs with <B>SGT-052</B> and <B>SGT-053</B> exhibit better light harvesting ability than the DSSCs with <B>SGT-012</B> and <B>SGT-016</B> porphyrins, due to the formation of the stronger intramolecular charge transfer complex. Thus, the incident photon-to-current conversion efficiency (<B>IPCE</B>) of <B>SGT-052</B> and <B>SGT-053</B>-based DSSCs was extremely red-shifted to a wavelength of 800 nm, resulting in higher <I>J</I> <SUB>sc</SUB> values of 15.3 and 14.6 mA cm<SUP>−2</SUP>, respectively. The DSSC utilising <B>SGT-052</B> and <B>HC-A1</B> exhibited a higher photovoltaic performance (<I>η</I> <SUB> <I>eff</I> </SUB> ∼9.6%) than did other sensitizers. On the basis of <B>SGT-052</B>-based DSSC, its DSSCs co-sensitized with <B>SGT-012</B> were prepared to improve the <I>J</I> <SUB>sc</SUB>, <I>V</I> <SUB>oc</SUB> and power conversion efficiency (10.2%).</P> <P><B>Highlights</B></P> <P> <UL> <LI> The influence of donor ability and bulkiness on the photophysical properties and cell performance of DSSCs was investigated. </LI> <LI> The triple bond at the porphyrin core and electron acceptor was introduced to extend the π-conjugation lengths. </LI> <LI> The co-sensitization strategy was conducted to further enhance the cell performances. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>