Abstract
Silver indium gallium di-selenide (AgIn0.8Ga0.2Se2) quaternary thin films have been grown onto ultrasonically and chemically cleaned glass substrates by three and four stage Stacked Elemental Layer Deposition (SEL) process. The stack of successively evaporated individual elemental layers was annealed in situ in the temperature ranging between 200oC and 350oC, for 15 min. Optical properties of the films have been ascertained by UV-VIS-NIR spectrophotometry (photon wavelength ranging between 300 and 2500 nm). The sharp descent of the transmission spectra reveals standard semiconducting nature that confirms the microstructural perfection of the films. Tuning of band gap is achieved for future tandem solar cells and various photovoltaic applications. The optical absorption behaviour above the fundamental absorption edge can be interpreted by considering the existence of at least two types of transitions: direct allowed and direct forbidden transitions. The former varies from 1.172 to 1.264 eV and the later varies as 1.49 to 1.67 eV, depending on annealing temperatures. Spin-orbit splitting of valence band due to spin-orbit interaction of electrons decreases with the increasing of annealing temperatures. The surface topography was studied at nanometric scale by atomic force microscopy (AFM). Urbach energy shows a minimum value at 300 oC.
Keywords
AgIn0.8Ga0.2Se2 thin film, Four stage film, Optical properties, Spin-orbit splitting, Urbach energy.
Citation
F. CHOWDHURY, J. BEGUM, M. S. ALAM, S. M. F. HASAN, Effects of annealing on the optical properties of AgIn0.8Ga0.2Se2 thin films, Optoelectronics and Advanced Materials - Rapid Communications, 4, 12, December 2010, pp.2039-2043 (2010).
Submitted at: Oct. 30, 2010
Accepted at: Nov. 29, 2010