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Low power conversion efficiency (PCE) and poor reproducibility are among the main challenges for tin-based perovskite solar cells (HPSCs). The facile formation of tin vacancies and oxidation of the divalent tin cation during the thin film fabrication process are among the causes of these problems, because the tin perovskite layer then becomes p-doped, resulting in significant trap-assisted recombination losses in devices. In this paper, we demonstrate that increasing the crystallinity of the tin perovskite film is an effective way to address the open issues with Sn-based perovskites. We succeed in improving the crystallinity of the 3D formamidinium tin iodide (FASnI 3) grains, increasing their size, and perfecting their orientation in the out-of-plane direction by incorporating ethylammonium iodide (EAI) into a 2D/3D tin perovskite film (where 2D is PEA 2 FASn 2 I 7 , PEA = phenylethylammonium). This leads to a decrease of traps and background charge carrier density, and therefore to decreased charge recombination losses in EA x 2D/3D based devices, as compared not only to devices based on FASnI 3 but also to those based on 2D/3D mixtures. As a consequence, devices using a perovskite layer with composition EA 0.08 2D/3D exhibit much higher PCE (8.4%) and better reproducibility compared to devices based on mixed 2D/3D perovskites (7.7%) and 3D perovskite (4.7%). Image 1 ● The crystallinity and orientation of the 3D formamidinium tin iodide grains is improved by incorporating ethylammonium cation into a 2D/3D tin perovskite film. ● The trap density and background charge carrier density are reduced by incorporating ethylammonium cation into a 2D/3D tin perovskite film. ● The charge recombination is reduced in the tin perovskite solar cells by incorporating ethylammonium cation into a 2D/3D tin perovskite film. ● The devices using ethylammonium modified 2D/3D tin perovskite layer exhibit much higher PCE (8.4%) and better reproducibility compared to devices based on either 2D/3D perovskites (7.7%) or 3D perovskite (4.7%) [ABSTRACT FROM AUTHOR]

A cold-rolled Ti-V high strength low alloy (HSLA) steel was isothermally annealed at 650 °C and 700 °C for different times. A unique combination of techniques including visible light microscopy (VLM), transmission electron microscopy (TEM), matrix dissolution, small angle neutron scattering (SANS) and hardness measurement has been employed to investigate the evolution of microstructure, hardness and precipitate composition, size and volume fraction. Results show that recrystallization is completed after annealing 8 h at 650 °C and 30 min at 700 °C. Three types of precipitates were identified: large Ti(C,N), medium-size (Ti,V)(C,N) and small (Ti,V)C. The Ti/(Ti+V) atomic ratio in the (Ti,V)C precipitates decreases with increasing radius in the 1–15 nm range, which can be explained by the initial nucleation of a TiC-rich core. The average size of the (Ti,V)C precipitates increases, whereas the number density decreases during annealing. The volume fractions of the three types of precipitates were separately determined by the matrix dissolution method. The volume fractions of (Ti,V)C precipitates obtained by matrix dissolution are comparable even slightly more accurate than those obtained by SANS. The hardness first increases and then decreases when annealing at both temperatures, which can be correlated well with the observed microstructural and precipitate evolution. Unlabelled Image • Precipitate evolution was quantitatively characterized by three different state-of-the-art techniques. • Composition and lattice parameter change of ternary precipitates as function of radius was obtained in the 1-15 nm range. • Matrix dissolution allowed separate volume fraction determination of three types of precipitates with different size ranges. • Precipitate volume fractions obtained by matrix dissolution are slightly better than those by small angle neutron scattering. [ABSTRACT FROM AUTHOR]