A team of international researchers has simplified the deposition of thin films in the commercial production of TOPCon solar cells. Using a tunnel-type plasma-assisted industrial atomic layer deposition (PEALD) technique, the team was able to achieve an energy conversion efficiency of 22.8% on a 613 W TOPCon module comprising 60 cells.
According to pv magazine international.
A team of international researchers has fabricated a tunnel oxide passivated contact solar cell (TOPCon) using a new technique to control tunnel oxide deposition at the atomic scale.
“This new technology aims to solve the problems posed by conventional low-pressure chemical vapor deposition (LPCVD) processes,” researcher Liao Baochen explained to pv-magazine. These include high maintenance costs and low deposition rates, especially for in situ doping. »
The scientists described the proposed method as a novel tunnel-like plasma-assisted industrial atomic layer deposition (PEALD) technique. According to them, it can produce dense tunnel-shaped silicon oxide (SiOx) films of high quality, low cost and high yield.
According to the researchers, this method could easily be integrated into tunnel-type plasma-enhanced chemical vapor deposition (PECVD) systems used for the fabrication of single-crystal PERC solar modules.
“A single deposition tool is sufficient to achieve the deposition of all thin layers, which makes this manufacturing process more competitive than traditional methods,” said the researchers.
Scientists engineered the cell with an n-type G1 wafer with a thickness of 170 µm and an area of 440.96 cm². They deposited all the layers at a temperature of 200°C respecting a cycle of 25 seconds. They then controlled the SiOx thickness by adjusting the number of atomic layer deposition (ALD) cycles and then annealed all the samples in a tube furnace at 920°C for 45 minutes to facilitate crystallization and dopant activation.
Finally, the academics screen-printed the cells on both sides with aluminum-silver (Al-Ag) alloy paste for the front electrodes and Ag for the rear electrodes. Then they baked the devices to a maximum temperature of around 800°C in a fast-burning industrial oven.
The research team tested the cells under standard lighting conditions and the best performing device achieved a power conversion efficiency of 24.2%, an open circuit voltage of 42.65 V, a short current -17.74 Amp circuit and 81.0% fill factor.
Scientists also used 60 cells to build a 613W TOPCon module that achieved 22.8% efficiency, 41.21V open-circuit voltage, 18.17A short-circuit current, and 79.5% fill factor.
“The cells were laser cut in half and laminated on both sides with two tempered glass panels to form bifacial modules,” they said.
They presented their new manufacturing process in the article “Atomic scale controlled tunnel oxide enabled by a novel industrial tube-based PEALD technology with demonstrated commercial TOPCon cell efficiencies > 24%”, recently published in Progress in Photovoltaics.
The group of researchers includes scientists working at the University of Nantong in China, the Chinese cell manufacturer Tongwei, the Institute of Materials Research and Engineering (IMRE) in Singapore, the University of New South Wales (UNSW) in Australia as well that the module manufacturer Risen Energy installed in China.
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