Synthesis and characterization of In₂S₃: Na thin films prepared by vacuum thermal evaporation technique for photovoltaic applications

Photovoltaic and semiconductor materials laboratory National Engineering School of Tunis, Belvedere PO Box 37, 1002 Tunis, Tunisia

Corresponding author: timoumiabdelmajid@yahoo.fr

Received: 19 January 2008
Accepted: 11 February 2008
Published online: 30 April 2008

Abstract

In₂S₃ thin films containing different quantities of sodium have been synthesized by co-evaporation of sodium and In₂S₃ powder from separate sources using vacuum thermal evaporation method. Films were deposited on ordinary glass at 240 °C. The process of incorporation of sodium was studied as function of at.% Na. Films have been characterised by means of X-ray diffraction, SEM, EDAX and spectrophotometry. X-ray diffraction analysis confirmed the initial amorphous nature of deposited layers and revealed the formation of In₂S₃ as function of annealing layers containing sodium in nitrogen at 300 °C for 2 h. Energy Dispersive X-ray Analysis (EDAX) revealed the composition of the films as a function of the sodium incorporation. Surface Electron Microscopy showed that these films were granular and homogenous. The films have an n-type electrical conductivity and their optical direct band gap can be managed between 2.20 and 2.45 eV by controlling their sodium content. The variation of parameters for as-deposited and annealed films has been studied within at.% solid solution composition. Thin layers with homogeneous surfaces, direct band gap energy of about 2.45 eV for 4 at.% Na and 0.9 μm-thick have been achieved.