Abstract: Methods and systems of producing perovskite material, in which the nucleation and crystallization processes are decoupled and, hence, independently controlled resulting in highly uniform nucleation sites for subsequent crystallization of perovskites. Methods and systems for using perovskite material and mixed perovskite films for solar cells.

Abstract: Methods and systems of producing perovskite material, in which the nucleation and crystallization processes are decoupled and, hence, independently controlled resulting in highly uniform nucleation sites for subsequent crystallization of perovskites. Methods and systems for using perovskite material and mixed perovskite films for solar cells.

Abstract: A gas sensor may include a mat including nanofibers attached to a substrate layer, a first electrode in electrical communication with one end of the mat, and a second electrode in electrical communication with the other end of the mat. The sensitivity of the gas sensor for carbon monoxide at a concentration of 50 ppm in air, and at a temperature from about 20° C. to 26° C., is at least 1.29.

Abstract: An UV detector, comprising: a sapphire substrate; a high temperature AlN buffer layer grown on the sapphire substrate; an intermediate temperature GaN buffer layer grown on the high temperature AlN buffer layer; a GaN epitaxial layer deposited on the intermediate temperature GaN buffer layer; a Schottky junction formed on top of the GaN epitaxial layer; and a plurality of ohmic contacts also formed on top of the GaN epitaxial layer, wherein, the high temperature AlN buffer layer and the intermediate temperature GaN buffer layer together form a double buffer layer structure so as to improve the reliability and radiation hardness of the UV detector; and wherein the high temperature AlN buffer layer and the intermediate temperature GaN buffer layer are formed by RF-plasma enhanced MBE growth technology.

Abstract: An UV detector, comprising: a sapphire substrate; a high temperature AlN buffer layer grown on the sapphire substrate; an intermediate temperature GaN buffer layer grown on the high temperature AlN buffer layer; a GaN epitaxial layer deposited on the intermediate temperature GaN buffer layer; a Schottky junction formed on top of the GaN epitaxial layer; and a plurality of ohmic contacts also formed on top of the GaN epitaxial layer, wherein, the high temperature AlN buffer layer and the intermediate temperature GaN buffer layer together form a double buffer layer structure so as to improve the reliability and radiation hardness of the UV detector; and wherein the high temperature AlN buffer layer and the intermediate temperature GaN buffer layer are formed by RF-plasma enhanced MBE growth technology.

Abstract: Gallium nitride and its related alloys have attracted much attention due to their important optoelectronic applications in blue to UV range as well as in the area of high-temperature electronics. Due to significant mismatches in the lattice constants and coefficients of thermal expansion between the GaN material and the sapphire substrate, GaN films typically exhibit large defect concentration and residual strain. In the present invention, a 20 nm thick low-temperature buffer layer is first grown on the sapphire substrate at preferably 500° C. This is followed by the growth of an intermediate-temperature GaN buffer layer (ITBL) at preferably 690° C. Finally, the epitaxial GaN layer is grown on top of the ITBL at preferably 750° C. It is found that the film quality is significantly affected by the use of an ITBL.