Optoelectronic Effects of Copper–Indium–Gallium–Sulfur (CIGS 2 )-Solar Cells Prepared by Three-Stage Co-Evaporation Process Technology

In this paper, the performance of Cu-(In,Ga)-S 2 (CIGS 2 ) solar cells with adjusting composite [Cu]/([Ga] + [In]) (CGI)-ratio absorber was explored and compared through an improved three-stage co-evaporation technique. For co-evaporating CIGS 2 absorber as a less toxic alternative to Cd-containing film, we analyzed the effect of the CGI-ratio stoichiometry and crystallinity, and explored its opto-electric sensing characteristic of individual solar cell. The results of this research signified the potential of high-performance CIGS 2 -absorption solar cells for photovoltaic (PV)-module industrial applications. For the optimal CIGS 2 -absorption film (CGI = 0.95), the Raman main-phase signal (A1) falls at 291 cm −1 , which was excited by the 532 nm line of Ar + -laser. Using photo-luminescence (PL) spectroscopy, the corresponding main-peak bandgaps measured was 1.59 eV at the same CGI-ratio film. Meanwhile, the best conversion efficiency ( η = 3.212%) and the average external quantum efficiency (EQE = 51.1% in the visible-wavelength region) of photo-electric properties were achieved for the developed CIGS 2 -solar cells (CGI = 0.95). The discoveries of this CIGS 2 -absorption PV research provided a new scientific understanding of solar cells. Moreover, this research undeniably contributes to a major advancement towards practical PV-module applications and can help more to build an eco-friendly community.