Significant Influence of a Single Atom Change in Auxiliary Acceptor on Photovoltaic Properties of Porphyrin-Based Dye-Sensitized Solar Cells

Abstract

The rational design of porphyrin sensitizers is always crucial for dye-sensitized solar cells (DSSCs), since the change of only a single atom can have a significant influence on the photovoltaic performance. We incorporated the pyridothiadiazole group, as a stronger electron-withdrawing group, into the commonly well-established skeleton of D-porphyrin-triple bond-acceptor sensitizers by a single atom change for a well-known strong electron-withdrawing benzothiadiazole (BTD) unit as an auxiliary acceptor. The impact of the pyridothiadiazole group on the optical; electrochemical; and photovoltaic properties of D–π–A porphyrin sensitizers was investigated with comparison for a benzothiadiazole-substituted SGT-020 porphyrin. The pyridothiadiazole-substituted SGT-024 porphyrin dye was red-shifted so that the absorption range might be expected to achieve higher light harvest efficiency (LHE) than the SGT-020 porphyrin. However, all the devices were fabricated by utilizing SGT-020 and SGT-024, evaluated and found to achieve a cell efficiency of 10.3% for SGT-020-based DSSC but 4.2% for SGT-024-based DSSC under standard global AM 1.5G solar light conditions. The main reason is the lower charge collection efficiency of SGT-024-based DSSC than SGT-020-based DSSC, which can be attributed to the tilted dye adsorption mode on the TiO2 photoanode. This may allow for faster charge recombination, which eventually leads to lower Jsc, Voc and power conversion efficiency (PCE).

Influence of the π-Bridge-Fused Ring and Acceptor Unit Extension in D−π–A-Structured Organic Dyes for Highly Efficient Dye-Sensitized Solar Cells

“…All the SGT -organic dyes have sufficiently positive potentials than the [Co­(bpy) 3 ] 2+/3+ redox couple ( ca. 0.56 V vs NHE) for regenerating the oxidized dye . The zero–zero transition energies ( E 0–0 ) of SGT-137 , SGT-138 , SGT-150 , and SGT-151 are 1.90, 1.88, 1.89, and 1.85 eV, respectively.…”

“…Fortunately, it is controllable by the relaxation dynamics of SGT -dyes by an effective intermolecular interaction between the dye and the HC-A1 co-adsorbent. From this observation, the effective intermolecular interaction between the dye and the HC-A1 co-adsorbent is considered as an additional role of the HC-A1 co-adsorbent, which has multiple functions, such as light harvesting at shorter wavelengths to improve J sc and inhibiting the π–π stacking of organic dyes to increase V oc by preventing the charge recombination. ,, …”

Photoexcited Intramolecular Charge Transfer in Dye Sensitizers: Predictive In Silico Screening for Dye-Sensitized Solar Cell Devices

“…Dye-sensitized solar cells (DSSCs) were initiated after their first report by O’Regan and Grätzel in 1991, − and with this rapid development was observed in the DSSC owing to their low-cost materials, flexible designs, high performance, and stability under low- or diffuse light conditions . The research efforts are mainly focused on tailoring the efficiency and stability by designing new sensitizers, − modifying the semiconductor band gap, , and optimizing the redox couple, dye absorbance, and counter electrodes . The typical working process of the device starts with photoexcitation of the dye molecule (from Dye → Dye*/Dye + in nanoseconds).…”

“…The SM-315 dye reported by Mathew et al with 13% power conversion efficiency (PCE) and ZL001 and ZL003 by Zhang et al with 12.8% and 13.6% PCE, respectively, are considered highly efficient D– π–A dyes. To improve the efficiency further, there were variations in the structure such as D–A, D−π–π–A, D–A′−π–A, and D–D−π–A: − changes in the donor in order to extend the π-conjugation, π-spacer bearing a strong electron donor group and high molar absorption coefficient, , and acceptor and linker as a stronger electron-withdrawing group. ,− In addition to designing new dyes, new hole , and electron , transport materials were developed to show low glass transition temperatures, low melting points, and high solubility, leading to an increase in pore filling into the semiconductor film and increasing the surface area for the adsorption of the dye. At the end, the semiconductor layer with high dye loading as well as high light-harvesting efficiency capability will ensure the increase in the photocurrent density and the improved performance of DSSCs. , Hence, structural/chemical/electronic modifications in any of the components (like D, π, A, linker, interface, etc.)…”

Tellurium-Doped, Mesoporous Carbon Nanomaterials as Transparent Metal-Free Counter Electrodes for High-Performance Bifacial Dye-Sensitized Solar Cells

“…Conventional DSSC devices consist of the three following main components: a dye-absorbed TiO 2 photoanode, a redox couple (iodine: I − /I 3 − , cobalt: Co(bpy) 3 2+/3+ ) [8][9][10], and a counter electrode (CE).…”