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Despite the rapidly increased power conversion efficiency (PCE) of perovskite solar cells (PVSCs), it is still quite challenging to bring such promising photovoltaic technology to commercialization. One of the challenges is the upscaling from small-sized lab devices to large-scale modules or panels for production. Currently, most of the efficient inverted PVSCs are fabricated on top of poly[bis(4-phenyl)(2, 4, 6-trimethylphenyl)amine] (PTAA), which is a commonly used hole-transporting material, using spin-coating method to be incompatible with large-scale film deposition. Therefore, it is important to develop proper coating methods such as blade-coating or slot-die coating that can be compatible for producing large-area, high-quality perovskite thin films. It is found that due to the poor wettability of PTAA, the blade-coated perovskite films on PTAA surface are often inhomogeneous with large number of voids at the buried interface of the perovskite layer. To solve this problem, self-assembled monolayer (SAM)-based hole-extraction layer (HEL) with tunable headgroups on top of the SAM can be modified to provide better wettability and facilitate better interactions with the perovskite coated on top to passivate the interfacial defects. The more hydrophilic SAM surface can also facilitate the nucleation and growth of perovskite films fabricated by blade-coating methods, forming a compact and uniform buried interface. In addition, the SAM molecules can also be modified so their highest occupied molecular orbital (HOMO) levels can have a better energy alignment with the valence band maxima (VBM) of perovskite. Benefitted by the high-quality buried interface of perovskite on SAM-based substrate, the champion device shows a PCE of 18.47% and 14.64% for the devices with active areas of 0.105 cm2 and 1.008 cm2, respectively. In addition, the SAM-based device exhibits decent stability, which can maintain 90% of its initial efficiency after continuous operation for over 500 h at 40 ℃ in inert atmosphere. Moreover, the SAM-based perovskite mini-module exhibits a PCE of 14.13% with an aperture area of 18.0 cm2. This work demonstrates the great potential of using SAMs as efficient HELs for upscaling PVSCs and producing high-quality buried interface for large-area perovskite films.


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Self-assembled monolayer enabling improved buried interfaces in blade-coated perovskite solar cells for high efficiency and stability

Show Author's information Jie Zeng1,§Leyu Bi2,§Yuanhang Cheng1Baomin Xu4( )Alex K.-Y. Jen1,2,3( )
Department of Materials Science and Engineering, City University of Hong Kong, Kowloon 999077, Hong Kong, China
Department of Chemistry, City University of Hong Kong, Kowloon 999077, Hong Kong, China
Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon 999077, Hong Kong, China
Department of Materials Science and Engineering, Guangdong-Hong Kong-Macao Joint Laboratory for Photonic-Thermal-Electrical Energy Materials and Devices, Southern University of Science and Technology, Shenzhen 518055, China

§ Jie Zeng and Leyu Bi contributed equally to this work.

Abstract

Despite the rapidly increased power conversion efficiency (PCE) of perovskite solar cells (PVSCs), it is still quite challenging to bring such promising photovoltaic technology to commercialization. One of the challenges is the upscaling from small-sized lab devices to large-scale modules or panels for production. Currently, most of the efficient inverted PVSCs are fabricated on top of poly[bis(4-phenyl)(2, 4, 6-trimethylphenyl)amine] (PTAA), which is a commonly used hole-transporting material, using spin-coating method to be incompatible with large-scale film deposition. Therefore, it is important to develop proper coating methods such as blade-coating or slot-die coating that can be compatible for producing large-area, high-quality perovskite thin films. It is found that due to the poor wettability of PTAA, the blade-coated perovskite films on PTAA surface are often inhomogeneous with large number of voids at the buried interface of the perovskite layer. To solve this problem, self-assembled monolayer (SAM)-based hole-extraction layer (HEL) with tunable headgroups on top of the SAM can be modified to provide better wettability and facilitate better interactions with the perovskite coated on top to passivate the interfacial defects. The more hydrophilic SAM surface can also facilitate the nucleation and growth of perovskite films fabricated by blade-coating methods, forming a compact and uniform buried interface. In addition, the SAM molecules can also be modified so their highest occupied molecular orbital (HOMO) levels can have a better energy alignment with the valence band maxima (VBM) of perovskite. Benefitted by the high-quality buried interface of perovskite on SAM-based substrate, the champion device shows a PCE of 18.47% and 14.64% for the devices with active areas of 0.105 cm2 and 1.008 cm2, respectively. In addition, the SAM-based device exhibits decent stability, which can maintain 90% of its initial efficiency after continuous operation for over 500 h at 40 ℃ in inert atmosphere. Moreover, the SAM-based perovskite mini-module exhibits a PCE of 14.13% with an aperture area of 18.0 cm2. This work demonstrates the great potential of using SAMs as efficient HELs for upscaling PVSCs and producing high-quality buried interface for large-area perovskite films.

Keywords:

self-assembled monolayer, buried interface, perovskite solar cells, upscaling, blade-coating
Received: 03 March 2022 Revised: 06 May 2022 Accepted: 09 May 2022 Published: 12 May 2022 Issue date: June 2022
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Publication history

Received: 03 March 2022
Revised: 06 May 2022
Accepted: 09 May 2022
Published: 12 May 2022
Issue date: June 2022

Copyright

© The Author(s) 2022. Published by Tsinghua University Press.

Acknowledgements

Acknowledgements

A. K. Y. J. thanks the sponsorship of the Lee Shau-Kee Chair Professor (Materials Science), and the support from the APRC Grant of the City University of Hong Kong (No. 9380086), the GRF grant (No. 11307621) from the Research Grants Council of Hong Kong, Guangdong Major Project of Basic and Applied Basic Research (No. 2019B030302007), Guangdong- Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials (No. 2019B121205002).

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