A team of international researchers has simplified the deposition of thin films in the commercial production of TOPCon solar cells. Using an industrial tube-type plasma-assisted atomic layer deposition (PEALD) technique, they achieved a power conversion efficiency of 22.8% in a 60-cell, 613W TOPCon module.
From pv magazine Global
An international research team has fabricated a Tunneling Oxide Passive Contacts (TOPCon) solar cell using a new technique that enables control of tunneling oxide deposition at the atomic scale.
“This new technology aims to solve the problems posed by traditional low-pressure chemical vapor deposition (LPCVD) methods,” researcher Liao Baochen told pv magazine. “These are, among others, high maintenance costs and low deposition rates, especially for on-site doping.”
The scientists described the proposed method as an innovative plasma-assisted industrial atomic layer deposition (PEALD) technique. They claimed that it can provide high-quality, dense tunnel-shaped silicon oxide (SiOx) films at low cost and high performance.
They stated that it could be easily integrated into the tubular-type PECVD systems used for the manufacture of monocrystalline PERC solar modules.
“A single deposition tool is enough to complete the deposition of all thin-film layers, making its fabrication process more competitive than conventional methods,” the researchers said.
The group constructed the cell using an n-type G1 wafer with a thickness of 170 μm and an area of 440.96 square centimeters. They deposited all the films at a temperature of 200 C and a cycle time of 25 seconds. Next, they controlled the thickness of the SiOx by adjusting the number of atomic layer deposition (ALD) cycles and annealed all samples in a tube furnace at 920 C for 45 min to facilitate crystallization and dopant activation.
As a final step, the researchers screen-printed the cells on both sides with a paste of aluminum-silver alloy (Al-Ag) for the front electrodes and Ag for the back electrodes. They then fired the devices at a maximum temperature of about 800 C using an industrial flash-fire 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 42.65V, a short circuit current of 17.74V. A and a fill factor of 81.0%.
The scientists also used 60 cells to build a 613 W TOPCon module that achieved an efficiency of 22.8%, an open circuit voltage of 41.21 V, a short circuit current of 18.17 A, and a fill factor of 79.5%.
“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 the new manufacturing process in “Atomic scale controlled tunnel oxide enabled by a novel industrial tube-based PEALD technology with demonstrated commercial TOPCon cell efficiencies > 24%”. demonstrated commercial efficiencies of TOPCon cells > 24%), which was recently published in Progress in Photovoltaics.
The group consists of academics from Nantong University, Chinese cell manufacturer Tongwei, Singapore’s Institute for Materials Research and Engineering (IMRE), Australia’s University of New South Wales (UNSW), and Chinese cell manufacturer risen energy modules.
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