Xinyi Jin

Single-crystalline lead halide perovskite arrays for solar cells

We have successfully grown single-crystalline lead halide perovskite arrays on a poly(3,4-ethylene dioxythiophene):polystyrenesulfonic acid (PEDOT:PSS) coated ITO substrate by the droplet-pinned crystallization (DPC) method and, for the first time, single-crystalline perovskite solar cells have been fabricated with a power conversion efficiency of 1.73%.

Constructing bulk-contact inside single crystals of organic semiconductors through gel incorporation

Single crystals of organic semiconductors are promising for high-performance semiconducting materials by virtue of their superior charge mobilities. Interfacing these single crystals with other foreign materials is needed to fabricate varied electronic devices. However, it is difficult to construct interfaces inside a single crystal that is typically homogeneous. In this work, single crystals of two typical organic semiconductors, anthracene and 9,10-diphenylanthracene, were grown from both silica gels and phenyl-modified silica gels. X-ray diffraction analysis demonstrated their single crystallinity. Examination of the residues which remained after sublimation of the gel-grown crystals revealed that the single crystals grown from phenyl-modified silica gels incorporated the gel networks, with the gel networks penetrating through the crystal in three-dimensional space, whereas the silica gel-grown crystals did not. This discrepancy suggests that the affinity between the crystal and the gel network favours gel incorporation. As such, our work provides a potential way to fabricate bulk contact between single crystals of organic semiconductors and foreign materials through gel crystallization.

Gel network incorporation into single crystals grown by decomplexation method

Crystallization in gel media has been occasionally found to result in single crystals with gel networks incorporated inside, extending the gel method with a long history for crystallization into a platform to design the internal composite structures of a crystal. The limited number of gel-incorporated crystals has inspired the investigation on how general gel incorporation is. Crystallization in gels through decomplexation has been widely used to grow crystals with extremely low water solubility, while whether the gel networks are incorporated inside these crystals has not been studied. In this work, crystals of AgCl, AgI and CuCl have been grown in both agarose gels and silica gels by decomplexation. The crystallographic structures of the crystals were identified by powder and/or single X-ray diffraction. The internal hybrid structures were studied by examining the residue materials after gentle etching and complete dissolution of the crystals. When grown from agarose gels containing self-assembled fibrous structures, gel networks were incorporated into single crystals of all the three compounds. In sharp contrast, the gel networks were pushed away when the crystals were grown in silica gels. The discrepancy between the crystals grown from agarose gels and those from silica gels is consistent with the effect of gel strength on gel incorporation. This work may help to harvest gel-incorporated crystals.

Optimal load resistance of a randomly excited nonlinear electromagnetic energy harvester with Coulomb friction

A nonlinear electromagnetic energy harvester directly powering a load resistance is considered in this manuscript. The nonlinearity includes the cubic stiffness and the unavoidable Coulomb friction, and the base excitation is confined to Gaussian white noise. Directly starting from the coupled equations, a novel procedure to evaluate the random responses and the mean output power is developed through the generalized harmonic transformation and the equivalent non-linearization technique. The dependence of the optimal ratio of the load resistance to the internal resistance and the associated optimal mean output power on the internal resistance of the coil is established. The principle of impedance matching is correct only when the internal resistance is infinity, and the optimal mean output power approaches an upper limit as the internal resistance is close to zero. The influence of the Coulomb friction on the optimal resistance ratio and the optimal mean output power is also investigated. It is proved that the Coulomb friction almost does not change the optimal resistance ratio although it prominently reduces the optimal mean output power.

PbI2 band gap engineering by gel incorporation

Incorporation of guest materials into semiconducting single crystalline hosts leads to the formation of semiconducting single-crystal composites. However, limited efforts have been made to comprehensively investigate the property of these potential functionalized single-crystal composites. Herein, PbI2/gel single-crystal composites have been successfully prepared. Diffuse reflectance spectra show a clear increase in the band gap of PbI2 after gel incorporation. The band gap is further increased through expanding the area of host/guest interfaces or enhancing the interatomic forces at the interfaces. The interatomic forces (electrostatic interaction) at the host/guest interfaces are attributed to this band gap shift. As such, this study provides a novel and facile way for band gap engineering by gel incorporation.