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German scientists have developed a solar cell with multiple quantum wells that allow higher levels of photocurrent. The device, with an efficiency of 3.4%, could be used in glass facades of buildings and windows, solar roofs of vehicles and greenhouses for agrovoltaics.
Researchers at the German Aerospace Center (DLR) have fabricated a semi-transparent solar cell based on ultrafine amorphous multiple quantum wells (MQWs) hydrogenated from silicon and germanium (Si/Ge).
“Our novel semi-transparent solar cell technology could offer various integration opportunities in various applications, such as glass facades in buildings and windows, solar roofs in vehicles, and greenhouses for agrivoltaics,” researcher Hosni Meddeb told pv magazine . “Custom design capabilities could enable multifunctional utilization beyond solar energy harvesting, such as aesthetics, visual comfort, and thermal management.”
Quantum wells are fine nanostructures inserted into cell layers to alter bandgap and other properties. In previous photovoltaic research, these nanostructures were used as simple quantum wells (SQW) and the novelty of this research consists in giving them a "multiple" configuration.
“This allows an extra degree of freedom for both optical design and bandgap engineering,” say the scientists, noting that MQWs offer advantages for both PV performance and transparency.
They built several solar cells with MQWs or SQWs and compared their performance under standard lighting conditions to assess the extent of the benefits brought by the former. They deposited the front and back electrodes by direct current magnetron sputtering technique and fabricated the semiconductor functional layers by plasma-enhanced chemical vapor deposition (PECVD) method at low temperature of 13.56 MHz. cells at 100 C for 30 min.
According to the researchers, a cell built with six 2.5-nanometer MQWs performed better in terms of open-circuit voltage and fill factor than a device based on a 20-nanometer SQW. The champion cell achieved a power conversion efficiency of 3.4% and an average visible transmission level of around 33%.
"A light-harvesting efficiency of more than 1.1% is achieved, which can be considered one of the highest among inorganic semitransparent solar cell technologies," they explained.
The research group described the cell technology in “ Novel semi-transparent solar cell based on ultrathin multiple Si/Ge quantum wells ”, recently published in Progress in Photovoltaics. He is currently trying to establish a techno-economic and ecological assessment for the application of his novel semi-transparent solar cell technology in building-integrated photovoltaics. More non-technical considerations and detailed cost estimates are expected in the future.
“The ultra-thin photovoltaic film concept we are proposing could offer promising technological advantages in terms of low material consumption, speed of fabrication, and cost reduction,” explains Meddeb. “Coupled with the cost-effective and industry-compliant manufacturing process, large-scale modularization is similar to that of mature thin-film PV technologies. This would facilitate the transfer of technology towards the level of manufacture and commercialization”. |
