Effect of different annealing conditions on CdZnTe thin films for absorber layer applications

Abstract

The Silicon based single junction and perovskite solar cells have demonstrated high efficiency but Silicon based cells suffer from the drawback of higher cost and perovskite solar cells are not stable and degradable in environment. The thin film based CIGS and CdTe cells have achieved efficiency of more than 22% but, particularly, the CdTe thin film solar cells require a suitable back contact which can be obtained by doping of Zn element in CdTe. The grain growth in CdTe-based films is attained by chloride treatment and therefore, in order to seek applicability of chloride treatment on CdZnTe (CZT) thin films, the present communication reports an evolution of different annealing conditions (in air, CdCl2 and MgCl2 environments) on physical properties to electron beam evaporated CdZnTe thin films. The XRD diffractograms revealed to the dominance of cubic phased peak corresponding to (111) plane and augmentation in grain size with treatment temperature. The optical spectra indicated variation in absorbance and transmittance with temperature of treatments and Tauc's plots demonstrated band gap of all the films in 1.41–1.55 eV range. Current-voltage characteristics divulged Ohmic character of films where conductivity and resistivity are eventually modified with annealing conditions. The FESEM micrographs of pristine films represented bouncy grains with some vacant spaces whereas chloride treated films showed larger grains. The EDS patterns confirmed the deposition of CdZnTe thin films and treatments concerned. The AFM maps demonstrated deep valley-like and hill-like configurations of processed films. The obtained results signify that the films annealed at 300 °C aver their suitability for absorber layer roles in development of efficient solar cells with single junction and tandem architectures.