Yeungnam University

About: Yeungnam University is a education organization based out in Daegu, South Korea. It is known for research contribution in the topics: Thin film & Catalysis. The organization has 9885 authors who have published 22075 publications receiving 372798 citations.

Flexible Cu 2 ZnSn(S,Se) 4 solar cells with over 10% efficiency and methods of enlarging the cell area

Abstract: For kesterite copper zinc tin sulfide/selenide (CZTSSe) solar cells to enter the market, in addition to efficiency improvements, the technological capability to produce flexible and large-area modules with homogeneous properties is necessary. Here, we report a greater than 10% efficiency for a cell area of approximately 0.5 cm2 and a greater than 8% efficiency for a cell area larger than 2 cm2 of certified flexible CZTSSe solar cells. By designing a thin and multi-layered precursor structure, the formation of defects and defect clusters, particularly tin-related donor defects, is controlled, and the open circuit voltage value is enhanced. Using statistical analysis, we verify that the cell-to-cell and within-cell uniformity characteristics are improved. This study reports the highest efficiency so far for flexible CZTSSe solar cells with small and large areas. These results also present methods for improving the efficiency and enlarging the cell area. Flexibility and homogeneity are preferred properties for the kesterite solar modules to compete with silicon counterparts. Here, Yang et al. achieve these properties by designing a thin and multi-layered precursor structure and at the same time increase the open circuit voltage and device efficiency.

DC-Link Capacitance Minimization in T-Type Three-Level AC/DC/AC PWM Converters

Abstract: In this paper, a novel control algorithm that minimizes the dc-link capacitance in the T-type three-level back-to-back converter is proposed. For this, the charging and discharging currents through the capacitor should be minimized, which can be achieved by utilizing the power balance of the ac/dc converter. Then, the voltage variation in the dc-link is also decreased, which makes a significant reduction in the size of dc-link capacitors. With this scheme, the electrolytic capacitors can be replaced by film capacitors, which are of higher power density, longer lifetime, and higher reliability. The effectiveness of the proposed strategy has been verified by the simulation and experiment results for a 3-kW T-type three-level ac/dc/ac pulsewidth modulation converter system with a 50- $\mu\hbox{F}$ film capacitor in the dc-link.