On the correlation between dye coverage and photoelectrochemical performance in dye-sensitized solar cells

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/)Concentration depth profiles of the ruthenium based dyes Z907 and N719 adsorbed onto titania are measured directly and used for determining the adsorption isotherm of the dyes. Dye layers formed by both grow in islands on the titania which do not cover the entire titania surface even at the maximum coverage. Impedance spectroscopy in conjunction with the adsorption isotherms shows that recombination losses mainly appear between the dye and the electrolyte solution. The short circuit current and the efficiency increase linearly with the dye coverage. The open circuit voltage slightly increases with increasing dye coverage which is interpreted as most likely to be a consequence of the higher charge in the particles upon higher dye loading on the TiO2 surface

Electrostatic interactions and physisorption: mechanisms of passive cesium adsorption on Prussian blue

The dangers posed by nuclear accidents necessitate developments in techniques for cesium removal. One such is the adsorption of cesium cations in Prussian blue (PB) materials, on which adsorption can be a substation process or pure physisorption. The underlying mechanism of the latter is not well understood, although a Langmuir isotherm is frequently used to model experimental results. In this work, we exploit tight-binding density-functional theory (DFTB) methods to probe the atomic interactions in the physisorption process. The results show that there is a diminishing return for the energy of adsorption as more sites are filled. This means that the adsorption sites are not independent, as stipulated by the ideal Langmuir isotherm. Instead, the results indicate that electrostatic effects need to be considered to explain the theoretical and experimental results. Therefore, an electrostatic Langmuir (EL) model is introduced, which contains an electrostatic ideality correction to the classic Langmuir isotherm. For future materials development, these physical insights indicate that shielding effects as well as the number of independent physical sites must be considered when synthesizing effective Prussian blue analogs (PBA). In conclusion, the study provides insights into the limiting mechanisms in the physisorption of cesium cations on PB.QC 20221201</p

Molten and Solid Trialkylsulfonium Iodides and Their Polyiodides as Electrolytes in Dye-Sensitized Nanocrystalline Solar Cells

Potential new electrolytes for dye-sensitized nanocryst. solar cells (DNSCs) of Graetzel type based on trialkylsulfonium iodides were studied. Room temp. molten salts of (Et2MeS)I, (Bu2MeS)I, and (Bu2EtS)I, with iodine in low concns., revealed good conducting abilities. DNSCs using iodine-doped (Bu2MeS)I as electrolyte achieved an overall light-to-electricity conversion efficiency of 3.7% in simulated AM 1.5 solar light at a light intensity of 0.1 Sun. The effects from varying the temp. during the I/V measurements were studied, as well as the effects of 4-tert-butylpyridine treatment of the electrodes

Photoelectrochemical studies of ionic liquid-containing solar cells sensitized with different polypyridyl-ruthenium complexes

The efficiency of dye-sensitized nanocryst. solar cells contg. ionic liqs., composed of org. sulfonium or imidazolium iodides, or a std. org. liq.-based electrolyte was studied, using sensitizers based on different polypyridyl-Ru complexes. The dyes N-719, [cis-Ru(II)(H2dcbpy)2(NCS)2(TBA)2] and Z-907, [cis-Ru(II)(H2dcbpy)(dnbpy)(NCS)2], with Z-907 having a more hydrophobic character, as well as the bidentate β-diketonato complex, [(dcbpy)2Ru(acetylacetonate)]Cl-, was studied. Solar cells sensitized with N-719 were more efficient than the Z-907 cells for all electrolytes studied. Adding a co-adsorbent, the amphiphilic hexadecylmalonic acid (HDMA), to Z-907 solar cells contg. an org.-liq. electrolyte resulted in increased overall light-to-electricity conversion efficiencies from 3.7% to 4.0%, (100 W/m2, AM 1.5). Possibly this is caused by an insulating hydrophobic barrier formed to suppress unwanted electron losses. By applying TiO2 (P25) nanoparticles, assumed to support electron transfer reactions, to the org.-liq. electrolyte, the conversion efficiency increased from 4.1% to 4.6% (100 W/m2, AM 1.5). In 1000 W/m2 illumination, the highest overall short-circuit c.d., 9.3 mA/cm2, was achieved with the N-719 sensitized cells, with the TiO2 nanocomposite-contg. org. liq. electrolyte. For solar cells sensitized with N-719, Z-907 or the β-diketonato complex, and contg. imidazolium or sulfonium iodide ionic liqs., no improvement of the overall conversion efficiency was noticed on addn. of HDMA to the dye or nanoparticles to the electrolyte

Cross-linked sulfur-selenium polymers as hole transporting materials in dye-sensitized solar cells and perovskite solar cells,

Novel inverse-vulcanized polymeric sulfur–selenium materials (SeS2:S:DIB, where DIB=1,3-diisopropenylbenzene) have been prepared and utilized for solid-state dye-sensitized solar cellsand perovskite solar cells. Under standard AM 1.5G illumination (1000 Wm-2), a power conversion efficiency of 1.70% was recorded for polymeric sulfur–selenium–based (SeS2:S:DIB) solidstate solar cells, which is higher than that of polymeric sulfurbased (S:DIB) devices (1.09 %). For perovskite solar cells, a relatively high efficiency has been achieved for polymeric sulfur–selenium-based (SeS2:S:DIB) solar cells (10.21%) and polymeric sulfur-based (S:DIB; 7.32%) solar cells, respectively. The conductivity of the polymeric SeS material has been determined to 2.2410-4 Scm-1, which is higher than for the polymeric sulfur material under the same doping conditions. Photoinduced absorption and steady-state photoluminescence measurements were performed to investigate the charge-transfer properties relevant for the solar cells. The results in the present study qualify the new polymeric sulfur–selenium materials as candidates for low-cost hole-transport materials for photovoltaic devices.QC 20170714</p

The observation of nano-crystalline calcium phosphate precipitate in a simple supersaturated inorganic blood serum model - composition and morphology

Aim. Calcium phosphate deposition in blood vessels is correlated to increased mortality risk. In this study, the formation of solid calcium phosphate in an in vitro solution mimicking the inorganic part of blood serum was studied. Methods. The precipitates formed were analyzed using several experimental techniques, including infrared spectroscopy, Raman spectroscopy, X-ray energy dispersive spectroscopy, chemical analysis of combustion gases, thermogravimetric analysis, as well as transmission electron microscopy and scanning electron microscopy. Results. The results indicate a microscopically amorphous but nano-crystalline material with an overall apatite structure. A plausible stoichiometry was determined to Ca-5(PO4)(3)(HCO3)center dot 4H(2)O with an estimated solubility constant of 6.10(-39) (mol/L)(9). Bicarbonate in the water solution was shown to be essential for the precipitation, giving implications for in vitro studies. Conclusions. The calcium phosphate formed in this study shows many similarities to pathological calcium phosphates regarding composition, morphology and crystallinity. (Journal of Applied Biomaterials & Biomechanics 2009; 7: 13-22

Accelerated Discovery of Perovskite-Inspired Materials through Robotized Screening Including Solar Cell Characterization

Currently, there is a strong need to accelerate development of systematic and robotized procedures for discovery of photovoltaic materials in order to aid the transition toward the use of clean and sustainable energy sources. Perovskite-type materials represent a broad class of compounds that have recently attracted great interest for application as photovoltaic materials. Such materials offer a vast chemical and structural space, qualifying them as an interesting starting point for further exploration using robotized screening methods. In this work, the development and application of a robotized procedure for the screening and solar cell characterization of perovskite-inspired materials is presented. Several combinations of cationic dyes and metal halides were examined by using a fully automated robotic screening cycle, including solar cell characterization based on triple mesoscopic solar cell devices. It is shown that the presented methodology is promising for the detection of new photovoltaic materials, which is demonstrated by the discovery of a selection of photovoltaic candidates. Some of the discovered candidates, for instance [QR][PbI3], were further characterized theoretically and experimentally. The authors would like to express gratitude to the Swedish Foundation for Strategic Research (SSF), through grant FID15-0023, the ÅForsk Foundation, through grant 17-594, the Swedish Energy Agency, through Grant ID: 46379-1, the Swedish Research Council, through grant ID: 2016-03223, and the Swedish Chemical Society through the 2022 postdoctoral scholarship “Stiftelsen Bengt Lundqvists minne” for financially supporting this work.</p