Improvement of the crystallinity and efficiency of wide-gap CIGS thin film solar cells with reduced thickness

Abstract In this study, the thickness of the high-Ga content CuIn 0.5 Ga 0.5 Se 2 (CIGS) absorber is optimized for highly efficient wide-bandgap CISG solar cells. Wide-bandgap (1.3 eV) CIGS solar cell with the highest efficiency of 16.3% and short circuit current density (J SC ) of 31.4 mA/cm 2 is fabricated using a CIGS absorber as thin as 1.6 µm. The highest open circuit voltage (V oc ) of 762 mV is achieved using a 1.2 µm thick CIGS absorber without alkali post deposition treatment, but the efficiency is only 14.8% due to the low J SC . The crystallinity of the wide-bandgap CIGS absorber is enhanced gradually by reducing the thickness of CIGS absorber from 2.2 to 1.2 µm as confirmed by X-ray diffraction (XRD). The carrier collection length of the CIGS solar cells is found to increase gradually from thinning the CIGS absorber as revealed by scanning electron microscope equipped with electron-beam-induced current detector (SEM-EBIC).