Colloidal CuInSe2 nanocrystals and thin films for low-cost photovoltaics

We report on the synthesis of colloidal CuInSe2 nanocrystals (NCs) using simple solution-based method and its vacuum thermally evaporated films. The tetragonal phase CuInSe2 NCs grow in the shape of nanoparticles with diameter varies between 30 and 40 nm according to high resolution transmission electron microscopy and electron diffraction measurements. The deposited films have been annealed for different times (up to 45 min) in vacuum and at different temperatures (150–346 °C). Optical characterization of the CuInSe2 NCs films using UV–Vis-NIR absorption, transmittance, excitation and photoluminescence measurements were performed. Optical properties of the deposited CuInSe2 films were quantified using developed theoretical model based on transmission and reflectance data. We found a strong dependence of the structural, morphologies and optical absorption coefficient of the prepared films on both annealing temperatures and annealing times. A remarkable enhancement of the optical absorption coefficient (α ∼ 3 × 105 cm−1) of the formed CuInSe2 NCs films with annealing was demonstrated and suggested the potential use of colloidal CuInSe2 for low cost photovoltaics.