Metal Precursor Influence on Performance of CuIn_1-xGa_xSe₂ Films

CuIn_1-xGa_xSe₂ (CIGS) films were prepared by a two-stage method, in which Cu-In-Ga metallic precursors were firstly deposited on unheated Mo-coated soda lime glass substrates by direct current sputtering CuGa (20%Ga) and radio frequency sputtering In targets inan Ar atmosphere, followed by selenization at 520 oC for 40 min in Se vapor. By adjust-ing the sputtering thickness ratio of surface CuGa (20%Ga) and bottom CuGa (20%Ga) alloy layers in metal precursor, different CIGS thin films were fabricated. Through X-ray diffraction spectra, Raman spectra, local energy dispersive spectrometer, planar- and cross-sectional views of scanning electron microscopy measurements, it revealed that the CIGS thin films from selenization of metal precursor with CuGa:In:CuGa thickness ratio of 7:20:3 (sample-2-se) was of chalcopyrite structure with the preferred (112) orientation, and the grains sizes ranged from 0.5 μm to 2 μm, and sample-2-se had no binary compound phase of In-Se and order defect compound phase. Consequently, the results of illuminated current-voltage curve and quantum efficiency measurements showed that the CIGS film device made from sample-2-se had relative higher photo-electric conversion efficiency (3.59%) and good spectrum response.