Impact of Alkali Post Deposition Treatment on Chalcogenide Based CIGSSe Solar Cells through Solution Based Method

Solution-based fabrication methods for high efficiency CIGSSe [Cu(In,Ga)(S,Se)2] solar cells have been extensively studied as the preference to vacuum-based fabrication methods. We employed an environmentally conscious solution-based deposition technique to fabricate thin films of CIGSSe. Despite significant research on non-vacuum (solution- processed) CIGSSe solar cells, compared to vacuum-based solar cells, their power conversion efficiency (PCE) remains lower. Additionally, numerous solvents employed in solution-based precursors are not environmentally friendly. We have developed a distinctive technology called solution-processed alkali (Sodium, Na) post-deposition treatment (PDT), which utilizes de-ionized (DI) water in ambient air. The presence of additional Na inclusions was found to significantly enhance the photovoltaic performance. The favorable effects of extra treatment were systematically investigated using several characterization approaches. Defect passivation had a positive impact, leading to PCE above 11% (in the absence of an anti-reflection coating layer).