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A method for in situ Al 2 O 3 incorporation into a Cu 2 ZnSn(S,Se) 4 (CZTSSe) absorber and its effect on solar cell performance is reported. Al 2 O 3 -incorporated CZTSSe films can be prepared by spraying a precursor solution containing Al metal salt dissolved together with Cu, Zn, and Sn metal salts and thiourea. X-ray photoemission spectroscopy (XPS) and field-emission transmission electron microscopy (FESEM) reveal the existence of an Al 2 O 3 phase in the CZTSSe film. X-ray diffraction (XRD) and Raman spectroscopy indicate that Al 2 O 3 incorporation (Al: 0%-2%) does not have a noticeable effect on the crystallization process through postselenization and does not change the lattice parameters of the selenized CZTSSe. However, optimal Al 2 O 3 incorporation is found to reduce the defect level and defect density, as confirmed by various characterization methods, such as 442 nm Raman spectroscopy, photoluminescence, admittance spectroscopy, and temperature-dependent current density measurements. In addition, Al 2 O 3 incorporation reduces the Urbach energy and back-contact barrier height. Al 2 O 3 incorporation is found to induce enhancement of Na and O concentrations in the absorber, which facilitates defect passivation effects. Owing to the observed beneficial effects of Al 2 O 3 incorporation, the device performance is significantly enhanced, achieving a maximum power conversion efficiency of 11.76%.

Impact welding is a material processing technology that enables metallurgical bonding in the solid state using a high-speed oblique collision. In this study, the effects of thickness of the flier and collision angle on weld interface morphology were investigated through the vaporizing foil actuator welding (VFAW) of AA1100-O to AISI 1018 Steel. The weld interfaces at various controlled conditions show wavelength increasing with the flier thickness and collision angle. The AA1100-O flier sheets ranged in thickness from 0.127 to 1.016 mm. The velocity of the fliers was directly measured by in situ photon Doppler velocimetry (PDV) and kept nearly constant at 670 m/s. The collision angles were controlled by a customized steel target with a set of various collision angles ranging from 8 deg to 28 deg. A numerical solid mechanics model was optimized for mesh sizes and provided to confirm the wavelength variation. Temperature estimates from the model were also performed to predict local melting and its complex spatial distribution near the weld interface and to compare that prediction to experiments.