Strategies to Enhance the Performance of Cu(In,Ga)(S,Se)2 Thin-Film Solar Cells by Doping Approaches

Abstract

With the deepening climate emergency and the growing imperative to move beyond fossil fuels, Cu(In,Ga)(S,Se)₂—commonly referred to as CIGS—thin-film solar cells are gaining prominence as a key pillar in the quest for long-term energy sustainability. Recently, CIGS solar cells have gained substantial recognition after achieving an impressive efficiency of over 23.6%. Despite this advancement and high-efficiency, the significant costs and technical complexities involved still pose major challenges to large-scale commercialization in vacuum-based processes. Solution-processed CIGS solar cells are being presented as a viable alternative to overcome these issues. This process allows for the formation of consistent thin films across large surfaces while also showing promise for reducing production costs. However, efficiency remains a key challenge and continues to be a critical factor for commercialization. The doping of new elements in CIGS absorber is an effective way to address these issues, significantly enhancing the performance of CIGS solar cells. Over the years, many elements have been incorporated into vacuum-based processes through doping, significantly contributing to high efficiency. Most notably, Uppsala University (UU) recently achieved a record efficiency of 23.6% by incorporating Sodium (Na), silver (Ag), and Rubidium (Rb). These findings imply that doping could potentially serve as a major catalyst for maximizing efficiency in solution-processed solar cells. This article reviews the latest developments in CIGS solar cells technology, summarizing the highest recorded efficiencies resulting from specific dopant incorporation strategies and combinations. Furthermore, we propose strategic approaches to improving the efficiency of solution-processed CIGS solar cells and discuss potential future research directions.