Low-volatility Electrolyte Research Articles

Electrochemical analysis of dye sensitized solar cell employing indoline-based and ruthenium-based dye combined with volatile and low-volatility solution-based electrolyte

In this study, the photovoltaic performances of dye-sensitized solar cells (DSSCs) have been studied for four different configurations involving two dyes (indoline-based, D205 dye, and ruthenium-based, N719 dye, respectively) and two types of electrolyte (volatile and low viscosity-based electrolyte, AN-50, and low-volatility and high-viscosity based electrolyte, Z-50, respectively). The electron transport and recombination properties in DSSCs have been investigated by electrochemical impedance spectroscopy, intensity-modulated photo-voltage spectroscopy and charge extraction methods. The D205 dye outperformed the N719 counterpart when the low-volatility electrolyte, Z-50, was employed, and similar performances between the two dyes were shown for the AN-50 electrolyte employment. The electron diffusion length was found to be positively correlated with and mainly responsible for the cells’ performances. Different dyes and/or electrolytes employment which was likely altered TiO2 nanoparticle’s surface properties were found to give influence on the electron transport properties inside the nanostructured film in this study.

Single-Layer TiO2 Film Composed of Mesoporous Spheres for High-Efficiency and Stable Dye-Sensitized Solar Cells

Mesoporous TiO2 spheres with high crystallinity and large specific surface area were facilely prepared via sol–gel and solvothermal methods. By tuning the time and temperature of the solvothermal process, the specific surface area and pore size of TiO2 spheres were fine-controlled without any additives. Compared with the dye-sensitized solar cell (DSC) based on the commercial P25 nanoparticles, the dye-sensitized solar cell employing optimized TiO2 spheres achieves an excellent efficiency of 10.3%, due to the outstanding dye-loading and light-scattering abilities as well as attenuated charge recombination. Furthermore, an impressive efficiency of 11.2% can be obtained after TiCl4 post-treatment. More importantly, in combination with a single-layer TiO2 film composed of mesoporous spheres and low-volatility electrolyte, the DSC exhibits high efficiency and long-term durability.

A methylene bridged bisimidazolium iodide based low-volatility electrolyte for efficient dye-sensitized solar cells

In this paper, we demonstrate that 1,1′-methylene bis(3-n-methylimidazolium) diiodide (MMIDI) can be used as an excellent alternative iodide source to conventional lithium iodide (LiI) in electrolyte for dye-sensitized solar cell (DSSC). The MMIDI is cheaper and shows much improved physical and chemical stability compared to LiI. Noticeably, smaller charge transfer resistance for the reduction of triiodide and longer electron lifetime are found in the DSSCs based on MMIDI electrolyte, which result in a 23% higher overall conversion efficiency (5.26%) than that based on LiI electrolyte (4.27%). When the initial MMIDI electrolyte is optimized with functional additives, a promising 6.24% conversion efficiency is achieved.

Ruthenium Sensitizer with Thienothiophene-Linked Carbazole Antennas in Conjunction with Liquid Electrolytes for Dye-Sensitized Solar Cells

A new heteroleptic ruthenium complex, coded CYC-B12, incorporating an antenna ligand composed of sequential connections of a thienothiophene conjugated bridge and carbazole hole-transport moiety was prepared. This new sensitizer exhibits a lower energy MLCT band centered at 555 nm with a high molar absorption coefficient of 2.24 × 104 M–1 cm–1. The device sensitized by CYC-B12 in conjunction with a volatile electrolyte shows a high photovoltaic efficiency of 9.4% under an illumination of standard global AM 1.5G sunlight. With a low-volatile electrolyte, the cell based on this new sensitizer shows not only a good conversion efficiency of 8.2% but also excellent durability (>96%) under light soaking at 60 °C in a simulated sunlight for 1000 h. The difference in the electron recombination kinetics caused by various liquid electrolytes or aging process is also investigated by employing the transient photoelectrical measurements.

A Thiophene‐Based Anchoring Ligand and Its Heteroleptic Ru(II)‐Complex for Efficient Thin‐Film Dye‐Sensitized Solar Cells

AbstractA novel heteroleptic RuII complex (BTC‐2) employing 5,5′‐(2,2′‐bipyridine‐4,4′‐diyl)‐bis(thiophene‐2‐carboxylic acid) (BTC) as the anchoring group and 4,4′‐ dinonyl‐2,2′‐bipiridyl and two thiocyanates as ligands is prepared. The photovoltaic performance and device stability achieved with this sensitizer are compared to those of the Z‐907 dye, which lacks the thiophene moieties. For thin mesoporous TiO2 films, the devices with BTC‐2 achieve higher power conversion efficiencies than those of Z‐907 but with a double‐layer thicker film the device performance is similar. Using a volatile electrolyte and a double layer 7 + 5 μm mesoporous TiO2 film, BTC‐2 achieves a solar‐to‐electricity conversion efficiency of 9.1% under standard global AM 1.5 sunlight. Using this sensitizer in combination with a low volatile electrolyte, a photovoltaic efficiency of 8.3% is obtained under standard global AM 1.5 sunlight. These devices show excellent stability when subjected to light soaking at 60 °C for 1000 h. Electrochemical impedance spectroscopy and transient photovoltage decay measurements are performed to help understand the changes in the photovoltaic parameters during the aging process. In solid state dye‐sensitized solar cells (DSSCs) using an organic hole‐transporting material (spiro‐MeOTAD, 2,2′,7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene), the BTC‐2 sensitizer exhibits an overall power conversion efficiency of 3.6% under AM 1.5 solar (100 mW cm−2) irradiation.

Highly Efficient Light-Harvesting Ruthenium Sensitizer for Thin-Film Dye-Sensitized Solar Cells

A high molar extinction coefficient heteroleptic ruthenium complex, incorporating an electron-rich hexylthio-terminal chain, has been synthesized and demonstrated as an efficient sensitizer for dye-sensitized solar cells. With this new sensitizer excellent power conversion efficiency is 11.5% and 4.7% obtained under an irradiation of full sunlight (air mass 1.5 global) in combination with a volatility electrolyte and solid state hole transporting material, respectively. The devices with low volatility electrolyte showed good stability under visible-light soaking at 60 degrees C during 1000 h of accelerated tests.

Design and synthesis of a novel anchoring ligand for highly efficient thin film dye-sensitized solar cells

A novel ligand, 5,5'-(2,2'-bipyridine-4,4'-diyl)-bis(thiophene-2-carboxylic acid) (BTC), and its Ru(II) complex (BTC-1) in which the anchoring group is attached to the thiophene units were developed. Using a low-volatility electrolyte and 3.3 mum mesoporous TiO2 films BTC-1 achieved a solar-to-electricity conversion efficiency of 6.1%, compared to 4.8% for N719 under the same experimental conditions.