Optimization of selenization process to remove Ga-induced pin-holes in CIGS thin films

In thin-film solar cells, deposition of pinhole and the crack-free absorber layer, with the right chemical stoi-chiometry is highly important for high-performance solar cell devices. In solution-based CIGS solar cell tech-nology, a nanoparticle ink approach provides phase stability of the final chalcogenide absorber layer. However, the sintering of small nanoparticles to form large grains with reduced grain boundaries is an important challenge in the fabrication process. This is usually realized by annealing in the Se atmosphere, i.e. selenization process. However, the presence of Ga in CIGS films leads to pinholes after selenization. In this study, the synthesis and deposition of high-quality films of CuInS2 (CIS) and CuIn0.75Ga0.25S2 (CIGS), are studied by using FESEM, XRD, EDS, and DLS characterization of CIGS and CIS nanoparticles and final films. We show that by selenization at reduced pressure and optimizing time and temperature, growing pinhole-free CIGS films with large grains is possible.

Automated summary

The synthesis and deposition of high-quality CIS and CIGS films were studied, and it was found that by optimizing the selenization process, pinhole-free CIGS films with large grains could be successfully obtained.