Platinum-free photoelectrochromic devices working with copper-based electrolytes for ultrastable smart windows

Photoelectrochromic systems are devices designed for large-scale manufacturing of smart windows, capable of changing their transmittance according to external environmental conditions. This communication proposes the replacement of the two most critical photoelectrochemical device components studied so far, namely the counter electrode and the redox mediator. Regarding the first, graphene nanoplatelets are used to replace platinum, maintaining both its optical and electrocatalytic properties, and at the same time reducing the device cost. Secondly, a copper-based redox pair was chosen to solve the corrosion problems typically encountered with the iodine-based mediator. The combination of the above components led to devices with high performance (coloration speeds in the order of seconds, with a maximum contrast ratio of 10.4 : 1), as well as the achievement of a long-term stability record (over 400 days) for these photoelectrochromic systems

PtSe(2 )outperforms Pt as a counter electrode in dye sensitized solar cells

International audienceIn the present study, we show that PtSe2 films, prepared by soft selenization of pre-deposited Pt, is a very efficient counter electrode (CE) in dye sensitized solar cells (DSSCs). Devices based on PtSe2 achieve better photoconversion efficiency (9.5 and PLUSMN; 1.2%) than those employing bare Pt CE (9.18 and PLUSMN; 0.21%), even if the latter use three times more Pt loading than that used to prepare the PtSe2 CE. Films with of various Pt loadings have been prepared by electrodeposition and their catalytic properties have been investigated and compared with films of corresponding Pt loading which have been transformed to PtSe2 by low-temperature selenization. The improved performance of the PtSe2 CEs has been assigned to the higher availability of catalytic active sites and the more effective mechanism of interfacial electron transfer. This is a first attempt to explore the role of PtSe2 as the CE in DSSCs. The strong advantages of PtSe2 in relation to catalytic activity, stability, efficiency, combined with cost reduction, due to the lower mass loading required for a given performance, renders this noble-transition metal dichalcogenide a promising candidate to boost the performance of third generation photovoltaics, opening-up possibilities, at the same time, for other applications where Pt is used as the catalyst

Photopolymers for smart windows

Smart windows are currently under intense investigation and thorough optimization in order to be effectively implemented in modern energy-saving buildings. The possibility of altering the light transmission properties of a window upon a voltage-, light-, or heat-induced external stimulus is a fundamental requirement to be pursued, and scientists are carefully investigating the quality, speed, and repeatability of the optical switching phenomenon. The resulting smart windows (often referred to as “building shells”) offer several advantages if compared to traditional ones, with a neat money saving for air-conditioning, heating, lighting, and curtains. A new photoelectrochromic device (PECD) is presented in this work proposing the combination of a WO3-based electrochromic device (ECD) and a polymer-based dye-sensitized solar cell (DSSC). In the newly designed architecture, a photocurable polymeric membrane is employed as quasi-solid electrolyte for both the ECD and the DSSC. In addition, a photocurable fluoropolymeric system is incorporated as solution-processable external protective thin coating film with easy-cleaning and UV-shielding functionalities. Such new polymer-based device assembly is characterized by excellent device operation with improved photocoloration efficiency and switching ability compared with analogous PECDs based on standard liquid electrolyte systems. In addition, long-term (>2100 h) stability tests under continuous exposure to real outdoor conditions reveal the remarkable performance stability of this new quasi-solid PECD system, attributed to the protective action of the photocurable fluorinated coating that effectively prevents photochemical and physical degradation of the PECD components during operation. This first example of quasi-solid PECD system paves the way for a new generation of thermally, electrochemically, and photochemically stable polymer-based PECDs, and provides for the first time a clear demonstration of their true potential as readily upscalable smart window components for energy-saving buildings

Photopolymers for smart windows

Smart windows are currently under intense investigation and thorough optimization in order to be effectively implemented in modern energy-saving buildings. The possibility of altering the light transmission properties of a window upon a voltage-, light-, or heat-induced external stimulus is a fundamental requirement to be pursued, and scientists are carefully investigating the quality, speed, and repeatability of the optical switching phenomenon. The resulting smart windows (often referred to as “building shells”) offer several advantages if compared to traditional ones, with a neat money saving for air-conditioning, heating, lighting, and curtains. A new photoelectrochromic device (PECD) is presented in this work proposing the combination of a WO3-based electrochromic device (ECD) and a polymer-based dye-sensitized solar cell (DSSC). In the newly designed architecture, a photocurable polymeric membrane is employed as quasi-solid electrolyte for both the ECD and the DSSC. In addition, a photocurable fluoropolymeric system is incorporated as solution-processable external protective thin coating film with easy-cleaning and UV-shielding functionalities. Such new polymer-based device assembly is characterized by excellent device operation with improved photocoloration efficiency and switching ability compared with analogous PECDs based on standard liquid electrolyte systems. In addition, long-term (>2100 h) stability tests under continuous exposure to real outdoor conditions reveal the remarkable performance stability of this new quasi-solid PECD system, attributed to the protective action of the photocurable fluorinated coating that effectively prevents photochemical and physical degradation of the PECD components during operation. This first example of quasi-solid PECD system paves the way for a new generation of thermally, electrochemically, and photochemically stable polymer-based PECDs, and provides for the first time a clear demonstration of their true potential as readily upscalable smart window components for energy-saving buildings

Photopolymers for stable solar cells, sodium batteries and photoelectrochromic windows

The stability of energy devices is a critical (but often disregarded) issue, since great focus is often devoted to the efficiency records (even if these values rapidly decrease upon time). However, today's research in the energy field must be connected to concepts such as long-term stability, safety and environmental impact. In this work, we present free-radical photopolymerization as an attractive technique for the design and straightforward preparation of polymeric components for different energy devices (both storage and conversion). Photopolymerization represents a very attractive technique to this purpose, since it does not require solvents, catalysts, thermal treatments and purification steps. In the initial section, polymer electrolytes for dye-sensitized solar cells (DSSC) are demonstrated as alternatives to the standard liquid counterparts, using cobalt complexes as redox mediator. In addition, external luminescent and light-cured coatings are developed to further increase cell durability through a combined effect of UV-cutting, down-shifting and self-cleaning. In the second section, electrolytes and light-cured protective coatings are demonstrated for the first time in photoelectrochromic devices, thus leading to smart windows with highly stable characteristics and easy to be manufactured on a large scale. Finally, we show how Na-ion polymer batteries can be considered as an emerging, green and safe solution to the large storage of the electricity produced by solar panels

Photopolymers for stable solar cells, sodium batteries and photoelectrochromic windows

The stability of energy devices is a critical (but often disregarded) issue, since great focus is often devoted to the efficiency records (even if these values rapidly decrease upon time). However, today's research in the energy field must be connected to concepts such as long-term stability, safety and environmental impact. In this work, we present free-radical photopolymerization as an attractive technique for the design and straightforward preparation of polymeric components for different energy devices (both storage and conversion). Photopolymerization represents a very attractive technique to this purpose, since it does not require solvents, catalysts, thermal treatments and purification steps. In the initial section, polymer electrolytes for dye-sensitized solar cells (DSSC) are demonstrated as alternatives to the standard liquid counterparts, using cobalt complexes as redox mediator. In addition, external luminescent and light-cured coatings are developed to further increase cell durability through a combined effect of UV-cutting, down-shifting and self-cleaning. In the second section, electrolytes and light-cured protective coatings are demonstrated for the first time in photoelectrochromic devices, thus leading to smart windows with highly stable characteristics and easy to be manufactured on a large scale. Finally, we show how Na-ion polymer batteries can be considered as an emerging, green and safe solution to the large storage of the electricity produced by solar panels

Photocatalytic Efficiency Tuning by the Surface Roughness of TiO2 Coatings on Glass Prepared by the Doctor Blade Method

A set of opaque films were prepared with Degussa P25® or Hombikat UV100® TiO2 powders by the doctor blade method on glass slides with different compositions of polyethylene glycol of 20 kDa (PEG20), and they were characterized by spectroscopy, microscopy and photochemical kinetics measurements. After annealing treatment at 450 °C, about 5–7% C atom was incorporated into the films, as a consequence of the degradation of the organic complexing agents, inducing a small reduction of the energy band gap of TiO2 (i.e. 3.02 ≤ Eg (eV) ≤ 3.08). All films were about 15 ± 2 μm thick but their micro-morphological characteristics depended on the content of PEG20, showing different patterns of cracks and aggregates that produce intense light scattering and retransmission phenomena with the result of a three-dimensional excitation of the TiO2 particles in the thick film. Back-face excitation with UVA light (365 ± 42 nm) of the opaque films in contact with an aqueous solution produced both surface-bound and free hydroxyl radicals (HO•), as detected using a coumarin solution as a radical dosimeter. The photogeneration efficiency of HO• decreased with the surface roughness of the films, which varied between 135 and 439 nm depending on the film's composition.Fil: Tulli, Fiorella Giovanna. Universidad Nacional de Santiago del Estero; Argentina. Universidad Nacional de Santiago del Estero. Instituto de Bionanotecnología del Noa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Bionanotecnología del Noa; ArgentinaFil: Morales, Jesús Marcelo Nicolás. Universidad Nacional de Santiago del Estero; Argentina. Universidad Nacional de Santiago del Estero. Instituto de Bionanotecnología del Noa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Bionanotecnología del Noa; ArgentinaFil: Salas, Esteban Eduardo. Universidad Nacional de Santiago del Estero; Argentina. Universidad Nacional de Santiago del Estero. Instituto de Bionanotecnología del Noa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Bionanotecnología del Noa; ArgentinaFil: Moran Vieyra, Faustino Eduardo. Universidad Nacional de Santiago del Estero. Instituto de Bionanotecnología del Noa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Bionanotecnología del Noa; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; ArgentinaFil: Borsarelli, Claudio Darío. Universidad Nacional de Santiago del Estero. Instituto de Bionanotecnología del Noa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Bionanotecnología del Noa; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Agronomía y Agroindustrias; Argentin