Scaffold-mediated tissue engineering has become a golden solution for the regeneration of damaged bone tissues that lack self-regeneration capability. A successful scaffold in bone tissue engineering comprises a multitude of suitable biological, microarchitectural, and mechanical properties acting as different signaling cues for the cells to mediate the new tissue formation. Therefore, careful design of bioactive scaffold macro-and microstructures in multiple length scales and biophysical properties fulfilling the tissue repair demands are necessary yet challenging to achieve. Herein, we have developed an antibacterial and biocompatible silica-silk fibroin (SF) gel-based ink through novel yet simple chemical approaches of sol−gel and self-assembly followed by processing the obtained gels as three-dimensional (3D) hybrid aerogel-based scaffolds exploiting the advanced materials design approaches of micro-extrusion-based 3D printing, and directional freeze-casting/drying approaches. As the main constituent of the hybrid biocompatible scaffold of this study, we used the SF extracted from Bombyx mori silkworm cocoon. However, to increase the cell responsivity and bactericidal efficiency of the final scaffold, thiol-ended antimicrobial and cell adhesive peptide sequence (SH-CM-RGD) was conjugated to silica-SF hybrid gels via covalent attachment using a spacer molecule through either preprint (prior to sol−gel) or during the post-printing steps on the previously printed silica-SF gel. In the next step, the hybrid Silica-SF-CM-RGD hydrogel ink was 3D-printed into the construct with interconnected porous structure with hierarchically organized porosity and a combination of several promising properties. Namely, due to the covalent linkage of the antibacterial peptide to the SF, the scaffold shows potent bactericidal efficiency toward Gram-positive and Gram-negative bacteria. Moreover, nanostructured silica components in the 3D-printed composites could intertwine with SF-CM-RGD to support the mechanical properties in the final scaffold and the final osteoconductivity of the scaffold. This study supports the promising properties of 3D-printed silica-SF-based hybrid aerogels constructs for repairing bone defect.

Silver bismuth iodide (SBI) materials have recently gained attention as nontoxic alternatives to lead perovskites. Although most of the studies have been focusing on photovoltaic performance, the inherent ionic nature of SBI materials, their diffusive behavior, and influence on material/device stability is underexplored. Herein, AgBi2I7, Ag2BiI5, and Ag3BiI6 thin films are developed in controlled ambient humidity conditions with a decent efficiency up to 2.32%. While exploring the device stability, it is found that Ag3BiI6 exhibits a unique ion‐migration behavior where Ag+, Bi3+, and I− ions migrate and diffuse through the dopant‐free hole transport layer (HTL) leading to degradation. Interestingly, this ion‐migration behavior is relatively fast for the case of antisolvent‐processed Ag3BiI6 thin‐film‐based devices contrasting the case of without antisolvent and is not observed for other SBI material‐based devices. Theoretical calculations suggest that low decomposition enthalpy favors the decomposition of Ag3BiI6 to AgI and BiI3 causing migration of ions to the electrode which is protected by using a thick HTL . The new mechanism reported herein underlines the importance of SBI material composition and fundamental mechanism understanding on the stability of Ag3BiI6 material for better solar cell design and also in extending the applications of unique ion‐migration behavior in various optoelectronics.

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Investigations on the effect of single or double A-site cation engineering on the photovoltaic performance of bismuth perovskite-inspired materials (A3Bi2I9) are rare. Herein, we report novel single- and double-cation based bismuth perovskite-inspired materials developed by (1) completely replacing CH3NH3+ (methylammonium, MA+) in MA3Bi2I9 with various organic cations such as CH(NH2)2+ (formamidinium, FA+), (CH3)2NH2+ (dimethylammonium, DMA+), C(NH2)3+ (guanidinium, GA+) and inorganic cations such as cesium (Cs+), rubidium (Rb+), potassium (K+), sodium (Na+) and lithium (Li+) and (2) partially replacing MA+ with Cs+ in different stoichiometric ratios. Compared to single-cation based bismuth perovskite devices, the double-cation bismuth perovskite device showed an increment in the device power conversion efficiency (PCE) up to 1.5% crediting to the reduction in the bandgap. This is the first study demonstrating double-cation based bismuth perovskite showing bandgap reduction and increment in device efficiency and opens up the possibilities towards compositional engineering for improved device performance. Graphic Abstract

Thin-film organic−inorganic hybrid perovskite (MeNH 3 PbI 3 ) solar cells have displayed remarkably high photoconversion efficiencies, making their net-shaping as flexible device elements desirable for a number of applications. Simulations show greatly enhanced light absorption in perovskite fibers in comparison to their thin-film counterparts, which demand the processing of hybrid perovskites in the one-dimensional morphology. We report here on the single-step fabrication of MeNH 3 PbI 3 nanofibers on a customized electrospinning process performed under inert conditions. Our results demonstrate reproducible synthesis of electrospun fiber mats in which the fiber dimensions were tailored by adjusting the polymer (PVP) content. Photoluminescence studies on the perovskite fibers revealed a blue shift of the emission peak possibly due to strain or charge confinement effects. The hybrid perovskite nanofibers offer promising applications in flexible and stretchable optoelectronics.