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The Chinese module manufacturer led an international research team seeking to save silicon material and increase efficiency in the development of heterojunction photovoltaic devices. The cell achieved a certified power conversion efficiency of 26.06% with a thickness of 57 µm, and the result was confirmed by the German Solar Energy Research Institute.
Researchers continue to push the limits of silicon solar cell technology as they strive to use less material in thinner, lighter cells without sacrificing efficiency or durability.
Now, a team led by researchers at Chinese vertically integrated module manufacturer Longi has developed processes to make high-efficiency heterojunction (HJT) solar cells, while avoiding the brittleness and lower efficiency results seen. in previous attempts to produce thinner cells.
In the study “ Flexible silicon solar cells with high power-to-weight ratios ,” published in nature , the scientists state that the thickness of the new cell ranges between 57 µm and 125 µm and is manufactured using M6 wafers with a surface area of ??274.4 cm2.
Thinning the wafers not only reduces weight and cost, but also facilitates charge migration and separation, the research team noted.
“The flexible and thin profile of these solar cells opens new opportunities to incorporate solar power generation into various aspects of daily life and industry in wearable electronics, building-integrated photovoltaics, transportation, space applications and emerging technologies with surfaces or structures. unconventional,” Xixiang Xu, head of Longi’s R&D team and corresponding author, told pv magazine .
The team developed its own control and regulation system to enable a continuous chemical vapor deposition (CVD) process with low-damage plasma to avoid epitaxy and maintain surface uniformity. This is a modification of the conventional step-by-step and non-continuous CVD process for passivation, the researchers noted.
Furthermore, they applied a “self-restoring nanocrystalline seeding process and vertical growth for doped contacts” in a high-frequency plasma-enhanced CVD (PECVD) process, which allowed the cultivation of “high-quality n-type and p-type carrier-selective contacts.” for the hole transport layer and the electron transport layers.
Another innovation was to use non-contact laser transfer printing to deposit low-shading grid lines. For the transparent conductive oxide (TCO) layers, they opted for cerium-doped indium oxide (ICO) and a low-damage reactive plasma deposition (RPD) process.
The team deposited ICO as the TCO coating using a low-damage reactive plasma deposition method, which they say “produced superior electrical performance, including much lower resistivity (2.7 × 10-4 O cm) and higher carrier mobility (83.1 cm V-1 s -1), compared to those of indium tin oxide derived from magnetron sputtering reported elsewhere,” adding that the process “played a decisive role in the subsequent “stability improvement.”
The cell achieved a certified power conversion efficiency of 26.06% at a thickness of 57 µm, a value of 26.56% at a thickness of 106 µm, and a maximum efficiency of 26.81% at a thickness of 125 µm. The 57 µm solar cell also had the highest power-to-weight ratio (1.9 W g-1) and open circuit voltage (761 mV).
The results were validated by the Hamelin Solar Energy Research Institute (Germany).
The scientists also managed to reduce optical losses by optimizing the configuration of the grating lines using an “industry-compatible non-contact” laser transfer printing technology. “The width of the fingers could be reduced from 40 µm (typical screen printing) to 18 µm, with the shading area controlled to less than 2%,” they noted.
According to the article, the devices were tested for potential- and light-induced degradation. “This technological advance provides a practical basis for the commercialization of flexible, lightweight, low-cost and highly efficient solar cells, and the possibility of folding or rolling crystalline silicon solar cells for travel is foreseen,” the team concludes.
The team consisted of researchers from Jiangsu University of Science and Technology and Curtin University. |
