Organic–inorganic lead halide perovskites have shown photovoltaic performances above 20% in a range of solar cell architectures while offering simple and low-cost processability. Despite the multiple ionic compositions that have been reported so far, the presence of organic constituents is an essential element in all of the high-efficiency formulations, with the methylammonium and formamidinium cations being the sole efficient options available to date. In this study, we demonstrate improved material stability after the incorporation of a large organic cation, guanidinium, into the MAPbI3 crystal structure, which delivers average power conversion efficiencies over 19%, and stabilized performance for 1,000 h under continuous light illumination, a fundamental step within the perovskite field.

Organic-inorganic hybrid perovskites have attracted significant attention owing to their extraordinary optoelectronic properties with applications in the fields of solar energy, lighting, photodetectors, and lasers. The rational design of these hybrid materials is a key factor in the optimization of their performance in perovskite-based devices. Herein, a mechanochemical approach is proposed as a highly efficient, simple, and reproducible method for the preparation of four types of hybrid perovskites, which were obtained in large amounts as polycrystalline powders with high purity and excellent optoelectronics properties. Two archetypal three-dimensional (3D) perovskites (MAPbI and FAPbI ) were synthesized, together with a bidimensional (2D) perovskite (Gua PbI ) and a "double-chain" one-dimensional (1D) perovskite (GuaPbI ), whose structure was elucidated by X-ray diffraction.

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The two-dimensional (2D) hybrid perovskites, in particular the Ruddlesden–Popper (RP) phase, exhibit excellent optoelectronic properties, higher flexibility in the employed large organic cations, and an enhanced stability against the environmental agents compared to the three-dimensional (3D) perovskites. However, the small organic cations inserted into the octahedral voids have been limited so far to those three fulfilling the Goldschmidt tolerance factor (t) despite the relaxed structure of the 2D RP perovskites. In this work, the incorporation of the large guanidinium (Gua) cation into the octahedral sites of the “perovskite slabs” has been explored for the first time in 2D RP perovskites. Thus, the methylammonium (MA) cation in the PEA2MA2Pb3I10 perovskite (PEA = phenylethylammonium) has been gradually substituted by the Gua cation to synthesize thin films of the mixed-cation PEA2(MA1–x Gua x )2Pb3I10 perovskite. X-ray diffraction (XRD) and grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements have revealed a regular expansion of the unit cell when increasing the Gua content up to 90%, proving the sequential insertion into the lattice of the Gua having a larger ionic radius than that of the MA cation. Furthermore, the preferential orientation of the PEA2MA2Pb3I10 perovskite films with the (hk0) planes parallel to the substrate is maintained up to a limit value of 60% Gua content. Importantly, the combined analysis of the steady-state and time-resolved absorption and photoluminescence (PL) spectra has revealed a change in the distribution of the n-members of the 2D RP perovskites toward phases with lower n values upon increasing the Gua content. The position and intensity of the photoluminescence can be modulated within the low-dimensional perovskites (n = 2, 3, 4, and 5) at high Gua content (≥70%). We have fabricated solar cells based on the mixed-cation PEA2(MA1–x Gua x )2Pb3I10 perovskites with power conversion efficiency (PCE) values similar to those of the reference cell (∼2.5%) up to percentages of Gua of 20%. The unencapsulated devices have shown a significant enhancement in the stability after 750 h, demonstrating the positive effect of the Gua cation on the degradation of the 2D RP perovskites.

Bioconjugates based on a redox protein and iron oxide magnetic nanoparticles were employed in the catalytic polymerization of phenylenediamines to obtain carbon-based fluorescent polymers.

Organic–inorganic hybrid perovskites have attracted significant attention owing to their extraordinary optoelectronic properties with applications in the fields of solar energy, lighting, photodetectors, and lasers. The rational design of these hybrid materials is a key factor in the optimization of their performance in perovskite‐based devices. Herein, a mechanochemical approach is proposed as a highly efficient, simple, and reproducible method for the preparation of four types of hybrid perovskites, which were obtained in large amounts as polycrystalline powders with high purity and excellent optoelectronics properties. Two archetypal three‐dimensional (3D) perovskites (MAPbI3 and FAPbI3) were synthesized, together with a bidimensional (2D) perovskite (Gua2PbI4) and a “double‐chain” one‐dimensional (1D) perovskite (GuaPbI3), whose structure was elucidated by X‐ray diffraction.

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