“N-i-p” Perovskite/Organic Hybrid Tandem Solar Cells Achieve Efficiencies Exceeding 23%

Engineers and materials scientists have been collaborating to create more sophisticated photovoltaic solutions, aiming to maximize the conversion of solar energy into electricity and contribute to the reduction of greenhouse gas emissions. As a result, various innovative solar cell designs, including all-perovskite tandem solar cells, have been introduced.

Recently, researchers at Chonnam National University in South Korea unveiled novel monolithic perovskite hybrid tandem solar cells built on all-inorganic halide perovskites. Highlighted in a paper published in Energy & Environmental Science, these solar cells have demonstrated promising efficiencies of 23%. Dr. Sawanta S. Mali, the first author of the paper, explained the limitations of single-junction solar cell designs, citing issues such as thermalization loss and transmission loss. To address these challenges, the researchers proposed the fabrication of tandem solar cells. These cells involve stacking two absorbers, namely wide bandgap (WBG) and narrow bandgap (NBG) materials, with the aid of a suitable interconnecting layer (ICL). While solar cell designs based on WBG materials have shown significant promise, many have relied on organic-inorganic hybrid perovskites, known for their thermal instability, potentially compromising overall performance. Furthermore, these solar cells often involve intricate fabrication processes, such as complex sputtering and atomic layer deposition (ALD) techniques, which can be challenging to implement and energy-intensive, especially on a large scale.

“In the context of narrow bandgap (NBG) materials, many researchers previously utilized Pb-Sn-based NBG, encountering severe degradation issues, such as the formation of Sn2+ to Sn4+,” explained Sawanta. “To circumvent these challenges, we devised all-inorganic perovskite-based wide bandgap (WBG) materials deposited in ambient conditions. This was achieved using our previously developed hot-air method, coupled with polymer bulk heterojunction (BHJ)-based narrow bandgap (NBG) materials for the construction of these monolithic two-terminal ‘n-i-p’ hybrid tandem solar cells (2T-HTSCs). Importantly, these cells can be manufactured using straightforward interconnecting layers (ICLs), eliminating the need for intricate sputtering or atomic layer deposition (ALD) processes.”

The primary goal of Sawanta’s recent research was to achieve thermally stable wide bandgap (WBG) materials that could undergo processing in ambient conditions and be seamlessly integrated into devices featuring a straightforward architecture, such as those adopting the n-i-p configuration. Ultimately, the team successfully synthesized their all-perovskite materials using a hot-air assisted spin coating technique. When incorporated into hybrid tandem solar cells with an n-i-p architecture, these materials demonstrated promising outcomes. The resultant solar cells achieved an efficiency of 23.07%, accompanied by an open-circuit voltage of 2.110 V. Impressively, they retained over 90% of their initial efficiencies throughout more than 600 hours of operation at their maximum power. “We implemented the n-i-p device configuration and an ambient air-processed approach, which is simple and conducive to future commercialization,” noted Sawanta. “Given that these 2T-HTSCs exhibit higher efficiency than single-junction counterparts with a very high open-circuit voltage (>2 V), we are considering implementing these cells in artificial photosynthesis, agri-voltaic applications, or Internet of Things (IoT).” Looking ahead, the materials developed by Dr. Sawanta S. Mali, Prof. Chang Kook Hong, and their team could be integrated into tandem solar cells with alternative designs to further assess their potential. Furthermore, the fabrication approach employed in this study offers a framework that other research teams can leverage to create robust materials for various photovoltaic applications. “As part of our recent study, we exclusively utilized double-junction-based tandem solar cells,” Mali explained. “In our forthcoming studies, we plan to extend this concept to triple or multijunction tandem solar cells (MJ-TSCs) and explore possibilities for upscaling.”

This article is republished from PhysORG under a Creative Commons license. Read the original article.

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