In the relentless pursuit of more efficient solar energy solutions, researchers have made a significant stride in enhancing the performance of wide-bandgap (WBG) copper indium gallium selenide (CIGS) solar cells. A study published in *Materials Futures* (translated from Chinese as *Materials Horizons*) reveals a novel approach to defect engineering through the co-doping of silver (Ag) and sodium (Na), offering a promising pathway to optimize both bulk and interfacial properties of these solar cells.
Dr. Weimin Li, the lead author from the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and his team have uncovered the intricate mechanisms behind the synergistic effects of Ag and Na co-doping. Their findings highlight that while both dopants reduce the Fermi level and enhance the built-in potential, they do so through distinct pathways. “Na increases carrier concentration but also raises interface defect density,” explains Dr. Li. “In contrast, Ag improves lattice ordering and reduces point defects, effectively suppressing interfacial defects and reducing recombination losses.”
The study demonstrates that Ag–Na co-doping improves both the open-circuit voltage (V_oc) and fill factor (FF) of WBG CIGS solar cells. However, the researchers found that excessive Na incorporation can introduce oversized conduction band offset (CBO) barriers, degrading device performance. To mitigate this issue, they proposed an Na-depletion strategy, reducing Na levels by 30% compared to the standard Ag-alloyed CIGS baseline. This approach achieved a balanced optimization of bulk carrier transport and interfacial band alignment, resulting in a champion power conversion efficiency (PCE) of 15.6%.
The optimized device showcased a V_oc of 801.4 mV, a short-circuit current density (J_sc) of 27.3 mA cm^−2, and a fill factor of 71.3%. Notably, the resulting bandgap energy of 1.36 eV closely aligns with the Shockley–Queisser model optimum, indicating a significant step forward in the development of high-performance WBG CIGS solar cells.
The implications of this research for the energy sector are substantial. As the demand for renewable energy continues to grow, the need for more efficient and cost-effective solar technologies becomes increasingly critical. The findings of Dr. Li and his team offer a viable pathway to enhance the performance of WBG CIGS solar cells, potentially reducing the cost of solar energy and making it more accessible.
“This research provides a deeper understanding of the cooperative effects of Ag and Na co-doping, paving the way for further advancements in defect engineering and solar cell optimization,” says Dr. Li. The study not only highlights the importance of interfacial and bulk defect management but also underscores the potential of innovative doping strategies in pushing the boundaries of solar cell efficiency.
As the energy sector continues to evolve, the insights gained from this research could shape the future of solar energy, driving the development of more efficient and sustainable technologies. The work published in *Materials Futures* serves as a testament to the ongoing efforts to harness the power of the sun more effectively, bringing us one step closer to a cleaner and more sustainable energy future.