Effect of Sensitizer Adsorption Temperature on the Performance of Dye-Sensitized Solar Cells

Abstract

Employing a mesoscopic titania photoanode whose bilayer structure was judiciously selected to fit the optoelectronic characteristics of the Ru-based heteroleptic complex Na-cis-Ru(4,4'-(5-hexyltiophen-2-yl)-2,2'-bipyridine)(4-carboxylic-acid-4'-carboxylate-2,2'-bipyridine)(thiocyanate)(2), coded as C101, we investigated the effect of temperature for dye adsorption on the photovoltaic performance of dye-sensitized solar cells (DSCs). We found a significant efficiency enhancement upon lowering the temperature applied during the sensitizer uptake from solution. When the dye adsorption was performed at 4 °C, the photovoltaic performance parameters measured under standard reporting conditions (AM1.5 G sunlight at 1000 W/m(2) intensity and 25 °C), i.e., the open circuit voltage (V(oc)), the short circuit photocurrent density (J(sc)), the fill factor (FF), and consequently the power conversion efficiency (PCE), improved in comparison to cells stained at 20 and 60 °C. Results from electrochemical impedance spectroscopy (EIS) and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) show that the self-assembled layer of C101 formed at lower temperature impairs the back-electron transfer from the TiO(2) conduction band to the triiodide ions in the electrolyte more strongly than the film produced at 60 °C. Profiting from the favorable influence that the low-temperature dye uptake exerts on photovoltaic performance, we have realized DSCs showing a power conversion efficiency of 11.5%.

Voltage enhancement in dye-sensitized solar cell using (001)-oriented anatase TiO2 nanosheets

“…Furthermore, there is no proportionality between the efficiency, η, and Г dye (Table 1). This finding is supported by Sauvage et al [31] who reported on decreasing efficiency for the C101-sensitized films, if the Г dye was larger than the monolayer coverage. They concluded that subtle structural characteristics at the C101/TiO 2 interface influence the electron transfer dynamics and light harvesting of the assembly [31].…”

“…The electrodes were soaked at room temperature in the solution overnight to secure complete attachment of the sensitizer dye to the electrode surface. To avoid irregularities in dye attachment [31], the sensitization time and temperature were identical for all the tested electrodes. The DSC was assembled with platinized F-doped tin oxide (FTO) counter electrode [32,33] …”

“…The found Г dye for (101) films is comparable to the values reported earlier for various Ru-bipyridine sensitizers adsorbed on titania (from 0.56 to 1.16 molecules/nm 2 ; see [38] for the data overview). Recently, Sauvage et al [31] studied the C101 dye adsorption on a TiO 2 film which was, obviously, rich in the (101)-terminated anatase particles. They found an almost perfect dye monolayer (assuming Г dye 00.57 molecules/nm 2 ) only for the films sensitized at low temperature (4°C), but the dye coverage exceeded the monolayer saturation limit for the films sensitized at room or higher temperatures.…”

A Review on Current Status of Stability and Knowledge on Liquid Electrolyte-Based Dye-Sensitized Solar Cells

“…1.0% Ga the -conjugation in the ancillary ligand not only exerts an energetic stabilization of the LUMO levels, thus redshifting the dye absorption, but also favorably affects the molar extinction coefficient of the dye reaching more than 20000 M −1 ⋅cm −1 [12,15,[112][113][114][115]. The integration of this second generation of dyes paved the way to improved performances in terms of light harvesting and power conversion efficiency.…”

“…Rapidly passing the threshold of 10% power conversion efficiency (PCE) in 1993 [10], despite endless efforts on material development, the efficiency had stagnated for a long time in the range of 11.0-11.5% [11][12][13][14][15][16] before scoring three new subsequent records, first 12.3% and 13.0% under A.M. 1.5 G conditions (100 mW/cm 2 ) using organic dye molecules in association with a stronger oxidant redox active cobalt polypyridyl complex [17,18]. More recently, certified 14.1% and even certified 17.9% PCE have been achieved by replacing the dye with a hybrid organic/inorganic lead halide perovskite absorber and the liquid electrolyte by a solid hole transporting material (HTM) [19,20] giving birth to a new technology called perovskite solar cells, for which progresses are remarkably fast.…”