Effect of milling time and heat treatment on the composition of CuIn0.75Ga0.25Se2 nanoparticle precursors and films

Abstract

Preparation of pure phase CuIn0.75Ga0.25Se2 nanoparticle powder by ball milling technique has been confirmed for the milling time of more than 45 min at 1200 rpm. Formation of shear bands responsible for breakdown of grains and generation of nanostructure during mechanical alloying, dislocation and defects induced due to milling has been studied by High-Resolution Transmission Electron Microscopy (HRTEM) analysis. Deviation in final composition of the products from those of starting materials has been discussed based on low volatilization of Se. Effect of milling time on the phase formation, particle size, and composition has been discussed in detail. Decrease in grain size from 12.44 to 7.96 nm has been observed with the increase in milling time. Mechanically induced self-propagating reaction mechanism which occurred during milling process is also discussed. Nanoparticle precursor was mixed with organic binder material for rheology of mixture to be adjusted for screen printing, and the films are subjected to heat treatment at five different temperatures in nitrogen ambient for 25 min. Average grain size calculated by Scherrer’s formula was almost the same irrespective of temperature. Reproducibility of precursor composition in the deposited films has been discussed in detail.