Exploring the impact of different annealing conditions on physical properties of CdSeTe thin films for solar cell absorber layer applications

Abstract

The perovskite and Silicon based single junction solar cells certainly showed higher efficiency but the perovskite solar cells are highly degradable and unstable in environment whereas conventional Silicon solar cells are relatively costly. The CdTe absorber based thin film solar cells have attained efficiency of greater than 22% where doping of Selenium into the CdTe absorber layer seems to improve the photovoltaic performance. The CdCl2 treatment is proven to be critical process which induces the grain growth and recrystallization in CdSeTe films. Thus herein, air and CdCl2 annealing is performed over thermally evaporated CdSeTe thin films to seek out their applicability as an effective absorber for Cd-based thin film photovoltaics. The XRD diffractograms exposed the appearance of cubic phase with (111) preferred orientation where crystallite size is increased with annealing temperature. The optical absorbance is found to be altered with temperature of annealing and Tauc’s plots exhibited that bandgap is found to be changed in the range of 1.40–1.52 eV with increasing annealing temperature. Electrical analysis divulges Ohmic character of films where electrical resistivity and conductivity are affected by nature and temperature of post-deposition annealing. The EDS patterns confirmed the deposition of CdSeTe thin films and post deposition CdCl2 activation treatment. The FESEM images demonstrated alteration in surface morphology by grain growth where the grain size of CdSeTe films is increased from 70 nm to 235 nm with CdCl2 annealing temperature. The findings confirm that annealed CdSeTe thin films showed demanding behavior for solar cell devices as prominent light harvesting absorber layers.