Researchers have made notable strides in enhancing the efficiency of kesterite (CZTSSe) thin-film solar cells. They introduced a novel technique for incorporating silver (Ag) into these solar cells, which helps minimize defects that can negatively affect their performance and encourages crystal growth, significantly boosting efficiency and setting the stage for commercial applications.
A group of experienced researchers, including Kee-jeong Yang, Dae-hwan Kim, and Jin-gyu Kang from the Division of Energy & Environmental Technology at DGIST (led by President Kunwoo Lee), worked together with Professor Kim Jun-ho’s team from the Department of Physics at Incheon National University and Professor Koo Sang-mo’s team from the Department of Electronic Materials Engineering. Their joint research led to substantial advancements in the performance of kesterite (CZTSSe) thin-film solar cells. They developed a new method for silver (Ag) doping to reduce defects obstructing cell performance and to foster crystal growth, which greatly enhances efficiency and opens up pathways for commercialization.
CZTSSe solar cells are made from a combination of copper (Cu), zinc (Zn), tin (Sn), sulfur (S), and selenium (Se). They are increasingly recognized as a low-cost, eco-friendly solar technology that uses abundant resources. This resource availability makes them more viable for large-scale manufacturing and competitively priced compared to traditional solar cells that rely on rare metals. However, standard CZTSSe solar cells suffer from low efficiency and significant current losses due to electron-hole recombination, which poses challenges for their commercial viability.
To tackle these challenges, the research team utilized a technique that involved doping the solar cell precursor with Ag. This Ag doping helps to reduce the loss of Sn and improves the mixture of materials at lower temperatures. As a result, crystal growth is accelerated, leading to fewer defects and better solar cell performance. The study meticulously examined how varying the placement of Ag within the precursor impacts defects and the properties of electron-hole recombination within the solar cells. The findings revealed that Ag can significantly boost solar cell performance by minimizing Sn loss and enhancing defect suppression.
Interestingly, the researchers discovered that improper placement of Ag can disrupt the formation of Zn and Cu alloys, causing Zn to gather in the bulk and create defect clusters. This misplacement can increase electron-hole recombination losses and lead to poorer performance. This insight underscores that the performance of solar cells is highly dependent on the specific placement of Ag doping.
Additionally, the study indicated that the liquid material created by Ag doping encourages crystal growth, which greatly enhances both the density and crystallinity of the absorber layer. This improvement results in a better energy band structure with fewer defects, facilitating smoother charge transport within the cell. These findings are poised to make a significant impact on the development of high-performance solar cells at a lower cost.
“In this study, we thoroughly examined the effects of Ag doping—an aspect that hasn’t been clearly defined before—process by process. We found that silver plays a crucial role in preventing tin loss and enhancing defect management,” stated Yang Kee-jeong, a senior researcher at the Division of Energy & Environmental Technology. “The findings provide valuable insights for designing silver-doped precursor structures aimed at increasing solar cell efficiency and are likely to aid in advancing various solar cell technologies.”
This research received funding from the Ministry of Science and ICT’s Source Technology Development (Leapfrog Development of Carbon Neutral Technology) Program and the Future-Leading Specialization Research (Grand Challenge Research and Innovation Project (P-CoE)) Program. The study has been published online in Energy & Environmental Energy (IF 32.4), a prominent international journal in the energy sector.
