Green zinc/galactomannan-based hydrogels push up the photovoltage of quasi solid aqueous dye sensitized solar cells

In the present work, we implement environmentally friendly water-based quasi-solid electrolytes (QSE) for dye sensitized solar cells (DSSCs), displaying an unprecedent open circuit voltage (VOC) as high as 750 mV. the production of the hydrogel for QSE-DSSCs is achieved by exploiting the concept of fully green design and fabrication, through the selection of components such as the natural polysaccharide galactomannan (GM), biocompatible zinc salts, and the employment of eco-friendly synthetic procedures to produce the hybrid gelating agents. In the process, moderate temperature (<40 °C), only aqueous solutions are employed, and, at most, ethanol is used in some phases of the procedure. depending on the type of the initial salt, either zinc hydroxysulfate lamellae or zinc oxide nanoparticles are created within the gel matrix, with a more extended nanoporous structure in the latter case. the nanostructures and the gels are investigated by multiple techniques, including X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Upon ensuing addition of I-/I3- redox mediator and assembling of the device, state-of-the-art aqueous QSE-DSSCs are achieved. The latter couples a 2 % efficiency (limited by charge diffusion as proved by electrochemical Impedance spectroscopy) with a good average visible transmittance (AVT), and light utilization efficiency (LUE), a couple of coveted features in wave-selective or semi-transparent devices. finally, linear response-time dependent DFT (LR-TDDFT) simulations are carried out on a model iodine/iodide layered zinc hydroxy sulphate structure towards a better understanding of the mechanism responsible for the high AVT

A new push–pull dye for semi-transparent p-type dye-sensitized solar cells: tuning conjugation by sexithiophene chain engineering

We report on the synthesis of two new dyes to be employed as sensitizers in p-type dye-sensitized solar cells (DSCs). The design of the two new molecules under consideration has been inspired by the state-of-art dye PMI-6 T-TPA. In particular, a specific engineering of the thiophene-based central core is here considered to favour structural planarity between an oligothiophenic π-spacer (a sexithiophene), and the acceptor and donor units made by peryleneimide (PMI) and triphenylamine (TPA) moieties, respectively. This leads to a wide absorption in the NIR with stabilization of the HOMO energy level in the resulting dyes, as supported by TD-DFT simulations and spectroscopic characterization. When tested as sensitizers in NiOx-based p-type DSCs, A6D (with an Acceptor-π-Donor structure) outperforms both its counterpart with a Donor-π-Donor structure (D6D) and P1, a benchmark dye in the field of p-DSCs. With A6D dye-sensitizer the resulting DSC device presents the quite remarkable value of stabilized efficiency as high as 0.15 % when I-/I3- is employed as redox couple and nanostructured NiOx photocathode is thick less than 2 μm and does not contain any blocking layer. Notwithstanding the panchromatic feature of the sensitizer, A6D-based devices show an average visible transmittance (AVT) of 8 %. Such a result paves the way toward the application of these types of multifunctional dyes in semi-transparent solar cells

Sustainable Thermosetting Polyurethane Resins as interlayers and primary Encapsulants in emerging photovoltaics

International audienceNowadays, polyurethane-based materials are massively exploited in a plethora of applications, from adhesives to foams, from building insulations to athletic tracks. Recently, the specifical use of aliphatic thermosetting polyurethanes (aPUs) has enormously increased in the industrial context for their versatile synthesis and tunable physicochemical properties. In the context of photovoltaics, and more specifically, the emerging field of Perovskite Solar Cells (PSCs), we proposed the use of thermosetting polyurethanes as low-cost but effective encapsulants on rigid devices. [1]The advantage of thermosetting PUs over other polymeric encapsulants lies in their tunable flexibility. Indeed, a properly designed combination of precursors leads to a PU that could be coupled with PET in flexible PSCs, allowing PU-protected devices to outperform the non-encapsulated cells in both conventional and high-humidity (RH > 70%) environments. Another possibility with thermosetting PU is their application as both encapsulant and interlayer in tandem devices; more in detail, we exploited a specifically designed formulation (i.e., having a refractive index comparable to the one of glass and a transmittance higher than 90%) to glue together a NIR-Dye Sensitized Solar Cell and a UV-absorbing PSC. The final tandem device reached a total efficiency close to 10% with an Average Visible Transmittance (AVT) as high as 35%, leading to a Light Utilization Efficiency close to 3.5%. All the proposed formulations have been engineered to improve their sustainability by replacing fossil fuel precursors with bio-based or waste-derived ones [2], thus leading to high-performing but sustainable encapsulants and interlayers for emerging photovoltaics