A group of international researchers has simplified the deposition of thin film layers in the commercial production of TOPCon solar cells. Using a tubular type of industrial plasma atomic layer deposition (PEALD), they were able to achieve a power conversion efficiency of 22.8% in 60-cell, 613W TOPCon modules.

From pv magazine global

An international research team fabricated a tunnel oxide passivated contacts (TOPCon) solar cell using a new technique that allows atomic-scale control of oxide tunneling deposition.

“This new technology is aimed at solving the problems faced by the traditional ones chemical vapor deposition at low pressure (LPCVD),” said researcher Liao Baocheng pv magazine. “These are, among other things, high maintenance costs and low siege speeds, especially for on-site doping.”

The scientists described the proposed method as innovative tube industrial plasma-assisted atomic layer deposition (PEALD) method. They claimed that it could produce high-quality dense tunneling films of silicon oxide (SiOx) at low cost and high throughput.

They said it could be easily integrated into tubular PECVD systems used to produce PERC monocrystalline solar modules.

A single deposition tool is sufficient to complete the deposition of all thin film layers, making the fabrication process more competitive than conventional methods,” the researchers said.

The group built the cell from an n-type G1 wafer 170 mkm and an area of ​​440.96 square meters. They deposited all films at a temperature of 200 C and a cycle time of 25 seconds. They then controlled the SiOx thickness 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 activation of the dopant.

As a final step, academics by screen printing cells on both sides using an aluminum-silver alloy paste (Al-Ag) for front electrodes and Ag paste for back electrodes. They then annealed the devices at a maximum temperature of around 800 C using an industrial rapid annealing furnace.

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 17.74A, and a duty cycle of 81.0%.

The researchers also used 60 cells to create a 613W TOPCon module that achieved an efficiency of 22.8%, an open-circuit voltage of 41.21V, a short-circuit current of 18.17A and a duty cycle of 79.5%.

The cells were laser-cut in half and laminated on both sides with two panels of tempered glass to form double-sided modules,” they said.

They introduced a new manufacturing process in “Atomic-scale controlled tunnel oxide thanks to new industrial tube-based PEALD technology with demonstrated commercial efficiency of TOPCon cells > 24%”, which was recently published in Progress in photovoltaics.

The group includes academicians from Nantong University, a Chinese cell manufacturer TongweiSingapore Institute of Materials Science and Engineering (IMRE), University of New South Wales (UNSW) in Australia and a Chinese module manufacturer Risen Energy.

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