CHEMICAL SCIENCE

Self-assembling single-molecule layers significantly improve solar cell efficiency and stability


Self-assembling single-molecule layers are now widely used in interface modification of electronic/optoelectronic devices. In view of this, on 12 May 2022, Alex K.-Y. Of the City University of Hong Kong was appointed as the 12th year of the Company. Professor Jen (Ren Guangyu) published a title in Nano Research Energy, an academic journal sponsored by Tsinghua University“Self-assembled Monolayer Enabling Improved Buried Interfaces in Blade-coated Perovskite Solar Cells for High Efficiency and Stability”Latest research results.

Figure 1: Perovskite solar modules prepared based on self-assembling single-molecule layer scraping. (a) Schematic diagram of the buried interface of the self-assembled single-molecule layer used to improve the perovskite film × prepared by scraping;

Perovskite solar cells have the potential to be a clean energy technology of the future due to their high performance and low cost characteristics. At present, the world’s highest efficiency of perovskite solar cells is 25.7%, which has exceeded the efficiency of polycrystalline silicon solar cells. However, due to the difficulty of scaling from small-area devices in the laboratory to large-area components required for commercial use, while ensuring good efficiency and stability, the commercial use of perovskite photovoltaic technology still faces great challenges. At present, most of the highly efficient inverted perovskite solar cells use poly[双(4-苯基)(2,4,6-三甲基苯基)胺](PTAA) as a lower hole transport material, but due to the poor wettability of PTAA, resulting in the upper layer scraping prepared large-area perovskite film is often uneven, and a large number of interfacial voids are introduced at the buried interface of the perovskite layer, which seriously damages the efficiency and stability of perovskite solar cells. Therefore, it is particularly important to study lower transport materials suitable for scraping and preparing large-area, high-quality perovskite films.

Alex K.-Y. City University of Hong Kong Professor Jen’s team has more than 10 years of research experience in the interface application field of self-assembled single-molecule layers to modified electronic devices/optoelectronic devices (Adv. Mater. 2008, 20, 2376. DOI: https://doi.org/10.1002/adma.200703050; Adv. Mater. 2011, 23, 1899. DOI: https://doi.org/10.1002/adma.201004762)。 The self-assembling monolayer is an ordered array of organic molecules that contain an anchored group that can bind to the substrate and a top functional group to regulate surface properties. These self-assembling monolayer molecules can act as intermediate connectors to achieve layer-to-layer tight bonding, regulate interface properties, and charge transmission. In the field of perovskite solar cells, the team has also reported that p-type and n-type self-assembling monolayers can effectively improve the performance of the device (ACS Nano 2014, 8, 12701. DOI: 10.1021/nn505723h; ChemSusChem 2017, 10, 3794. DOI: https://doi.org/10.1002/cssc.201701262)。

Therefore, based on the previous research experience, the team proposed the use of the above-mentioned PTAAs in the preparation of large-area perovskites in this work[2-(3,6-二甲氧基-9H-咔唑-9-基)乙基]Phosphonic acid (MeO-2PACz) replaces PTAA as a self-assembling single molecule hole extraction layer. On the one hand, the hydrophilic MeO-2PACz monolayer improves the nucleation and growth of scraped perovskite films, forms a dense and uniform submerged interface and promotes interaction with the top perovskite to passivate interface defects. On the other hand, since the MeO-2PACz self-assembles a single-molecule layer with only single-layer molecules, the carrier can be efficiently extracted from the perovskite to the substrate electrode by charge tunneling, thereby improving device performance. Thanks to the high-quality buried interface and efficient hole extraction of perovskites on the self-assembling single-molecule layer, the energy conversion efficiency of 18.47% and 14.13% was achieved on perovskite devices and components with an effective area of 0.105 cm2 and 18.0 cm2, respectively. In addition, perovskite solar cells based on self-assembled single-molecule layers exhibit good stability, maintaining an initial efficiency of 90% after more than 500 hours of continuous operation near the maximum power point in an inert gas atmosphere.

This work demonstrates the great potential of the self-assembling single-molecule layer as a carrier extraction layer in the application of scraping large-area perovskite solar cells. Recently, the team has also developed a co-assembled single-molecule layer strategy to improve the device performance and stability of perovskite solar cells (Angew. Chem. Int. Ed. 2022,DOI: 10.1002/anie.202203088)。 In the future, the research team will develop multi-functional self-assembled single molecules to achieve the synergy of charge extraction, interface regulation, and perovskite defect passivation through the design optimization of self-assembling molecules, and help the commercialization process of perovskite photovoltaics.

Related paper information:Jie Zeng, Leyu Bi, Yuanhang Cheng, Baomin Xu, Alex K.-Y. Jen. Self-assembled monolayer enabling improved buried interfaces in blade-coated perovskite solar cells for high efficiency and stability. Nano Res. Energy 2022, DOI: 10.26599/NRE.2022.9120004.

https://doi.org/10.26599/NRE.2022.9120004

As a companion issue to Nano Research, Nano Research Energy (ISSN: 2791-0091; e-ISSN:2790-8119; Official Website: https://www.sciopen.com/journal/2790-8119Founded by Tsinghua University in March 2022, Professor Chunyi Zhi of the City University of Hong Kong and Professor Qu Liangti of Tsinghua University co-editor-in-chief.《Nano Research Energy》It is an international multidisciplinary interdisciplinary, all-English open access journal, focusing on the cutting-edge research and application of nanomaterials and nanoscience in new energy-related fields, benchmarking international top energy journals, and committed to publishing high-level original research and review papers. Before 2023, the APC fee will be waived, and all teachers are welcome to submit articles. Please contact: NanoResearchEnergy@tup.tsinghua.edu.cn.

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