Crystallite size and intrinsic strain contribution in band gap energy redshift of ultrasonic-sprayed kesterite CZTS nanostructured thin films

Abstract

The effect of crystallite size and intrinsic strain on the band gap shift of ultrasonically sprayed Cu2ZnSnS4 films has been discussed. The films have been deposited over glass substrates under various temperatures, namely 280, 320, 360, and 400 °C. X-ray diffraction revealed the presence of kesterite single phase with preferential orientation along (112) plan. The band gap energy decreases from 1.84 to 1.51 eV with increasing substrate temperature, where an increase in crystallite size from 5.92 to 21 nm was observed as well as relaxation of intrinsic strain from 6.82 × 10−3 lines−2 m−4 to 2.11 × 10−3 lines−2 m−4. A concurrency behavior between crystallite size and intrinsic strain effect on the band gap shift has been noticed. The intrinsic strain effect is dominant in higher substrate temperature and that of crystallite size in low temperatures owing to the presence of a strong quantum confinement.