New research from Germany has shown that heterojunction solar cells with silver buyer on the front with silver buyer and silver pasta on the back an efficiency coping of 0.13% compared to the reference screen printed bifacial cells based on silver alone. The research group worked specifically on printing and screen printing as printing methods.
Researchers from the Forschungszentrum Jülich of Germany have shown that the heterojunction (HJT) solar cells with motorized with copper (CU) pasta or copper -silver (CUAG) pasta can achieve efficiency levels that are comparable to those of PV devices that have only been noticed with AG.
They explained that the HJT design is most suitable for reducing or eliminating silver use in solar cells, because the transparent conductive oxides (TCO) that are used in this architecture as barriers to prevent the diffusion of copper in silicon.
“CU is a viable alternative to AG and proves that the sustainable PV development goal of AG -use of 2 mg/w is realistic in 2030,” said the corresponding author of the research, Kinging Ding, said PV -Magazine. “Now we are planning to introduce Silver-free metallization in full solar modules and carries out reliability and stability studies under moisture heat and thermal cycli conditions. We also want to support Plug companies to develop new ideas and to optimize existing approaches to make CU paste to make costs competitive than AGCU paste. “
The research team in particular investigated three different cell designs: with metallization exclusively based on CU; with CUAG metallization; And with AG metallization. Screen Printing (SP) and dispensing were used to build the metal contacts, whereby the second technique was labeled as a low silver consumption capacity and a high aspect ratio.
“We made the front and back of the cells with meter with AG, AGCU and CU paste and compared them. In addition, finger characteristics such as width, height, line resistance, contact resistance and bulk resistance were evaluated,” the Academici explained that the tests were performed at 244.32 cm2 Bifacial solar cells with a waffle thickness of 135 μm. “We first printed the performance of the screen and released fingers from the three different pastas on one side of the waffle.”
Image: Forschungszentrum Jülich, Progress in Photovoltaics, CC by 4.0
They used the same screen design and 96 fingers with a pitch of 1.6 mm for all three pastas. Moreover, they used Single-Nozles dose to print them. The AGCU fingers were glowed with an oven and the CU fingers with a hot plate.
The production process was carried out at a temperature of 250 ° C, although the metallization of CU pasta usually requires 300 ° C, whereby the researchers identified the breakdown threshold at temperatures of more than 280 ° C for 5 s.
The analysis showed that the cells screen prints with AGCU paste on the front and AG pasta on the back achieved an average efficiency improvement of 0.13% absolutely absolutely absolutely compared to benchmark AG screen printing bifacial devices.
“Cells with screen -printed AGCU on the front and screen printed CU on the back achieved an efficiency of up to 23.6% absolute, only 0.35% lower than reference cells, while about 70% of AG Paste was saved,” the academicians emphasized. “In particular, cells with screen -printed CU on both sides achieved an average efficiency of 22.4% absolute and a maximum of 23.08% absolute, which represents the highest performance that was registered for cells with screen -printed CU on both sides and zero AG.”
They also discovered that CU achieved a better performance than CU SP.
“To maximize the potential of AGCU and CU pastas, it is essential to optimize and standardize CU screen printing and dispensing processes, reduce sealed finger widths and to conduct further research into printing processes, stability, reliability and economic benefits,” they concluded.
Their findings can be found in “Achieving high efficiency for silicon hetero junction solar cells using silver -free metallization“Published in Progress in photovoltaic.
Another research team of Forschungszentrum Jülich recently proposed to use Wire Bonding (DWB) as a method for low temperature for the mutual of finger-free HJT sun cells on the front with the help of cheap, very conducting CU-wires. Their analysis showed that a solar module built with the proposed solar cells achieved a power conversion -efficiency of 20.19%, which compared by 20.43% for a benchmark panel constructed with six conventional tabbing threads at the front.
This month, researchers from Ghent University in Belgium and the ENGIE Laborelec unit of the French energy giant announced that in 2030 they could be needed by the PV industry how much silver might be needed and have discovered that silver shortages could become more frequent.
Their analysis showed that the total silver demand is expected to reach 48,000 to 52,000 rpm in 2030, with the offer sufficient to reach only 34,000 row. In the meantime, the PV industry is expected to grow its silver demand in 2030 by a factor of 1.6 to 2.3 to 10,000-14,000 row, as a result of a higher silver consumption in new cell designs such as Topcon and HJT. “As a result, the silver demand from the PV industry could be 29-41 % of the expected offer in 2030,” they emphasized.
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