Single-material zinc sulfide bi-layer antireflection coatings for GaAs solar cells

• Published in: Optics express Vol. 21 Suppl 5; no. S5; pp. A821 - A828
• Main Authors: Leem, Jung Woo, Jun, Dong-Hwan, Heo, Jonggon, Park, Won-Kyu, Park, Jin-Hong, Cho, Woo Jin, Kim, Do Eok, Yu, Jae Su
• Format: Journal Article
• Language: English
• Published: United States 09-09-2013
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/oe.21.00a821

We demonstrated the efficiency improvement of GaAs single-junction (SJ) solar cells with the single-material zinc sulfide (ZnS) bi-layer based on the porous/dense film structure, which was fabricated by the glancing angle deposition (GLAD) method, as an antireflection (AR) coating layer. The porous ZnS film with a low refractive index was formed at a high incident vapor flux angle of 80° in the GLAD. Each optimum thickness of ZnS bi-layer was determined by achieving the lowest solar weighted reflectance (SWR) using a rigorous coupled-wave analysis method in the wavelength region of 350-900 nm, extracting the thicknesses of 20 and 50 nm for dense and porous films, respectively. The ZnS bi-layer with a low SWR of ~5.8% considerably increased the short circuit current density (J(sc)) of the GaAs SJ solar cell to 25.57 mA/cm(2), which leads to a larger conversion efficiency (η) of 20.61% compared to the conventional one without AR layer (i.e., SWR~31%, J(sc) = 18.81 mA/cm(2), and η = 14.82%). Furthermore, after the encapsulation, its J(sc) and η values were slightly increased to 25.67 mA/cm(2) and 20.71%, respectively. For the fabricated solar cells, angle-dependent reflectance properties and external quantum efficiency were also studied.