Within the first year of project, the work packages responsible for materials development (WP2 to WP4) initiated the preparation of the selected family of materials with enhanced properties. EPFL synthesized a triple Cs/MA(methylammonium)/ FA(formamidinium) cation perovskite achieving high efficient PSCs with a stabilized PCE of 21.1 %. These triple cation perovskites showed to be more robust to subtle variations during the fabrication process enabling a breakthrough in terms of reproducibility. Concerning lead-free absorber materials, two research lines were followed in parallel. IChF PAN synthesized by mechanochemistry bismuth based materials to replace lead in perovskites due to the same electron configuration of Pb2+ and Bi3+ ions. Present materials with composition of A3Bi2I9 like Cs3Bi2I9 or MA3Bi2I9 exhibit bandgaps in the range of 1.9 eV – 2.1 eV. A theoretical research line, based on photophysics properties of lead-free perovskites, have been extensively studied by CNRS partner, who identified tin-based divalent compounds likely to be the most relevant for lead free perovskite solar cells. Moreover, it was concluded that Cs–based compounds (namely CsSnI3) present two additional advantages: they have a slightly reduced band gap and are free from two scattering mechanisms present in hybrid halide perovskite compounds, namely molecular quasielastic relaxations and rotation-translation couplings. These two research lines will converge for assessing the lead-free absorber that really allows reaching the forecasted 16 % efficiency. Finally, mechanochemistry developed by partner IChF PAN was also applied to prepare high purity MAxFA1-xPbI3 hybrid perovskite absorbers and to assess the contour proportions of reactants for obtaining single-phase perovskites. Within WP3, it has been successfully synthesized and cha¬racterized the first series of low band gap HTMs: the S,N-heteroacene-based D-π-A HTMs, which showed excellent power conversion efficiencies close to 18 %. The second series was designed to lead to large band gap materials, where a synthetic route for the preparation of spiro-cyclopentadithiophene-based HTMs has been successfully established. The acridine-based HTM will be finished soon and the synthesis of the thioxanthene-based HTM has already started. Novel alternative to TiO2 scaffold materials that can act as electron contacts were developed within WP4. IChF PAN partner prepared novel zinc oxide (ZnO) nanostructures including: (i) carboxylate oligoethylene glycol (OEG-carboxylate) coated ZnO nanocrystals, as well as (ii) mesoporous structures composed of ZnO nanoparticles. Towards increasing the PSC device performance, polymer-templated nucleation and crystal growth of perovskite films were applied by EPFL partner. The incorporation of rubidium cations into perovskite solar cells allowed to reach a stabilized power conversion efficiency of 21.6 % with an open circuit voltage of 1.24 V by applying lithium doped TiO2 as scaffold material. Finally, UPORTO developed within WP5 a laser-assisted glass sealing process for bonding TCO-TCO glass substrates, soda-lime glass to TCO glass substrates and to bond glass to titanium coated glass substrates. The process temperature for sealing the above mentioned substrates was 120 °C and the substrates dimension was gradually increased from 5 × 5 cm2 up to 9 × 9 cm2 aiming the scale up of the laser-sealing process. The hermeticity and long-term stability laser-sealed empty cells was assessed, showing leak rates complying with the pertinent standards.
