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