Organic dyes have been studied for applications in large-area, flexible, cheap, and efficient organic electronic devices. Among them, diketopyrrolopyrrole (DPP) has gained attention thanks to its planar structure, photochemical and thermal stability, and easy processability. Also, the electron-withdrawing nature of DPP makes its application attractive in the synthesis of donor–acceptor (D–A) copolymers, with appealing features such as the tunable energy levels and photophysical and electrochemical properties. Inspired by these exciting characteristics, a copolymer was developed based on DPP, thiophene, and fluorene (PFDPP2T). Photophysical and electrochemical studies using both experimental and theoretical approaches were performed aiming to understand the properties of this material, such as, for instance, the D–A characteristic and the outstanding electrochemical stability upon oxidation that enables more than 400 cycles of p-doping. The outcomes unveil fundamental aspects of this class of copolymers, reinforcing their suitability for photo-electrochemical and optoelectronic applications.

We quantified the bulk Rashba splitting and suppression in polymorphs of MA­(Pb, Sn, Ge, or Si)­I3 perovskites. The low-computational-cost DFT-1/2 quasiparticle correction was performed for all structures, combined with the inclusion of spin–orbit coupling (SOC) effects. The presence of SOC and symmetry breaking from the metal off-centering octahedral distortion are indispensable and essential conditions for Rashba splitting, whose magnitude emerges from the Pb → Si sequence. Additionally, the quasiparticle correction provides energy bandgaps for MAPbI3 (cubic, tetragonal, and orthorhombic), MASnI3 (cubic and tetragonal), and MAGeI3 (cubic) that are in outstanding agreement with experimental results. However, while gap energies are yielded collaboratively from the metal off-centering and relative octahedral tiltings, the bulk Rashba suppression is reached for metal on-centering (octahedral platonic-like) configurations that are thermodynamically stable even when the charge polarization is kept invariant among metal–I bonds in the polymorphs.

Recent finds have revealed in metal halide perovskites the presence of lower local symmetry contributions especially in the cubic phase in detriment to its high symmetry monomorphic structure (Pm-3m). We analyzed the impact of the polymorphic nature in CsBX 3 inorganic perovskites (B = Ge, Sn, Pb; X = Cl, Br, I) through first-principle calculations to show how the polymorphism contributes more to the material stability than their monomorphic counterparts. Distinct stability trends can be seen for each halogen and metal series, revealing the role of the (strong) spin−orbit coupling (SOC) on the stability throughout the Ge → Sn → Pb sequence from a set of local motif contributions, such as distortions on the octahedrons, relative tiltings, Cs displacement, and metal offcentering networks. The combination of relativistic quasiparticle correction and SOC provided accurate values of gap energies, showing that the experimental measurement is actually an average from structural local motif contributions. At the same time, given the absence of a prohibited transition, a blue shift in the UV−vis spectra was observed for all chemical compositions from high symmetry structure → polymorphic version. This result revealed that a high suppression of the total optical absorption can be avoided through the replacement of the toxic Pb by greener alternatives, especially CsSnX 3 and CsGeX 3 (X = Br and I), providing a potential perspective to the market of solar cell devices.

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