Earth‐abundant and environmentally benign kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) is a promising alternative to its cousin chalcopyrite Cu(In,Ga)(S,Se)₂ (CIGS) for photovoltaic applications. However, the power conversion efficiency of CZTSSe solar cells has been stagnant at 12.6% for years, still far lower than that of CIGS (23.35%). In this report, insights into the latest cutting‐edge strategies for further advance in the performance of kesterite solar cells is provided, particularly focusing on the postdeposition thermal treatment (for bare absorber, heterojunction, and completed device), alkali doping, and bandgap grading by engineering graded cation and/or anion alloying. These strategies, which have led to the step‐change improvements in the power conversion efficiency of the counterpart CIGS solar cells, are also the most promising ones to achieve further efficiency breakthroughs for kesterite solar cells. Herein, the recent advances in kesterite solar cells along these pathways are reviewed, and more importantly, a comprehensive understanding of the underlying mechanisms is provided, and promising directions for the ongoing development of kesterite solar cells are proposed.

Tandem solar cells, which integrate multiple junctions, present a promising pathway to surpass the efficiency limits of single‐junction silicon (Si) solar cells. This article explores why Si is the optimal choice for the bottom cell in tandem configurations and examines various configurations and interconnection techniques that have been reported. It then reviews a range of photovoltaic (PV) technologies for the top cell, including well‐established III–V compounds and emerging materials like perovskites and chalcogenides PV materials, which are currently used or have potential for use in constructing Si‐based tandem cells. Additionally, the paper highlights the ongoing challenges faced by these top cells in Si‐based tandem technology. The aim of this review is to provide a comprehensive overview of different PV technological advancements and to identify strategic directions for future research that could lead to the development of highly efficient Si‐based tandem PV systems.

Selenium incorporation in Sb ₂ (S,Se) ₃ thin films suppresses grain coalescence and lowers grain boundary energy. This facilitates beneficial band bending and improved charge transport, clarifying the origin of enhanced photovoltaic performance.