No abstract

In this work, novel electrospun scaffolds with fibers oriented randomly and evenly in three dimensions (3D) including in the thickness direction were developed based on the principle of electrostatic repulsion. This unique structure is different from most electrospun scaffolds with fibers oriented mainly in one direction. The structure of novel 3D scaffolds could more closely mimic the 3D randomly oriented fibrous architectures in many native extracellular matrices (ECMs). The cell culture results of this study indicated that, instead of becoming flattened cells when cultured in conventional electrospun scaffolds, the cells cultured on novel 3D scaffolds could develop into stereoscopic topographies, which highly simulated in vivo 3D cellular morphologies and are believed to be of vital importance for cells to function and differentiate appropriately. Also, due to the randomly oriented fibrous structure, improvement of nearly 5 times in cell proliferation could be observed when comparing our 3D scaffolds with 2D counterparts after 7 days of cell culture, while most currently reported 3D scaffolds only showed 1.5- to 2.5-fold improvement for the similar comparison. One mechanism of this fabrication process has also been proposed and showed that the rapid delivery of electrons on the fibers was the crucial factor for formation of 3D architectures.

The efficiency and stability of perovskite solar cells are affected by the Pb–I antisite and uncoordinated Pb0 defects existing at the interface. Directional management of Pb-based defects can reduce the defect density and voltage loss. In this work, to settle the Pb-based defects at the interface for further stabilization of the perovskite surface, we propose the strategy of designing a low-dimensional perovskite (LDP) by an amphoteric heterocyclic cation which can increase the defect formation energies and inhibit the generation of Pb–I antisite defects. The growth of the mixed-phase LDP can introduce a strong interaction with undercoordinated Pb2+ upon the surface of peroskite films accomplished with the ability of dealing with different types of surface-terminating ends. The modified devices showed an increased efficiency of 24.07% (stabilized efficiency of 23.25%) as well as improved overall stability. This opens up a direction for prompting the practical application of perovskite photovoltaic devices based on the directional management of Pb-based interface defects.