Low-cost and high-performance poly(thienylene vinylene) derivative donor for efficient versatile organic photovoltaic cells
Graphical Abstract
A low-cost and high-performance PTV-derivative polymer (PTVT-BT) is designed and synthesized. PTVT-BT possesses strong crystallinity and high hole mobility. The OPV cell based on PTVT-BT:eC9 demonstrates a PCE of 16.31%. Besides, the PTVT-BT-based indoor OPV cell with 4 cm2 effective area shows a PCE of 26.07% (1000 lux). Importantly, the tandem cell with PTVT-BT as the donor of the sub-cell exhibits an outstanding PCE of 18.49%.
Introduction
The advantages of light-weight, rich molecular structures and highly-tunable photoelectric properties of organic semiconductors enable organic photovoltaic (OPV) cells not only show important application prospects in the efficient conversion of sunlight to electrical energy [1], [2], [3], [4], [5], [6], but also exhibit great application potentials in indoor photovoltaic applications, integrated applications of OPV-organic light-emitting diode (OLED) and flexible wearable electronic devices [7], [8], [9], [10], [11], [12], [13]. Over the past few decades, the power conversion efficiencies (PCEs) of both single-junction and tandem OPV cells have exceeded 19% [14], [15], [16]. However, these high-performance OPV cells generally use polymer donors with complex molecular structures, which inevitably increases the costs of OPV cells and is not conducive to their large-scale production [17], [18], [19]. Developing polymer donors with simple structures is a promising strategy to overcome this issue. However, such materials are very scarce. Currently, only PTQ-10 and PTVT-T have been reported as typical high-performance polymer donors with simple structures [20], [21]. Therefore, considerable efforts should be devoted to designing more low-cost polymer donors.
It is very challenging to design polymer donors with high-performance and low-cost characteristics. In terms of molecular structure, it needs to meet the following requirements: Ⅰ. Avoid using fused ring units. At present, high-performance polymer donors usually contain many fused ring units, because the fused ring structure is not only beneficial to the delocalization of π-electrons, but also can ensure that the molecules have planar backbones [22], [23]. However, the complex ring-closure reactions greatly increase the synthesis costs of materials [24]. For instance, with thiophene units as raw materials, dithiophene can be obtained only by one-step coupling reaction, while the seemingly simple bithiophene unit requires at least five chemical reactions to complete, and the yield is much lower than that of dithiophene [25], [26], [27]. However, non-fused ring units can not effectively ensure the flatness of molecular backbones and the stability of the molecular conformations. Thus, it is difficult to design high-performance polymer donors with non-fused ring units. Ⅱ. Avoid using expensive raw materials or functional groups. Previous studies have clearly shown that the price of raw materials largely determines the costs of the final products [27], [28]. Therefore, cheap raw materials should be used for molecular synthesis. In addition, the use of additional functional groups to modify molecular structures should be avoided to reduce the cost of material synthesis. For instance, halogen atoms are widely used to modify molecular structures to improve their optical, electrical and molecular packing properties [29]. However, the introduction of such functional groups will obviously increase the synthesis steps and difficulty. Therefore, on the premise of limited low-cost raw materials, it will be more difficult to obtain high-performance polymer donors without the modifications of functional groups.
In terms of molecular properties, high-performance polymer donors should have the following characteristics: Ⅰ. They should have strong solution aggregation effects. The molecules with solution effects can maintain ordered molecular aggregations during the transition from solution states to solid films, which is beneficial to the formation of high-purity phases and large-scale phase separation [30], [31]. However, the planarity of non-fused molecular backbone is difficult to control, thus it is difficult to obtain such polymer donors with strong solution aggregation effect. Ⅱ. Donor materials should have strong external quantum efficiencies of electroluminescence (EQEELs). The EQEEL of an OPV cell can reflect its non-radiative energy loss [32]. It has been proven that the EQEEL of the acceptor plays a decisive role in determining the EQEEL of the corresponding OPV cell [33]. Nelson et al. reported that, when the driving force is negligible, the first excited state (S1) of the donor and charge transfer (CT) state formed at donor/acceptor interface will be hybrid [34]. Therefore, the luminescence comes from the radiative recombination of electrons from the hybrid energy levels to the ground states. Thus, high EQEEL is also needed for the polymer donor to be used for fabricating OPV cell with low . However, the strategy for constructing OPV materials with high EQEELs has not been established. Therefore, using cheap structural units to design non-fused polymer donors with high EQEELs is very challenging.
In this work, based on our previously reported polymer donor PTVT-V, we designed and synthesized a high-performance polymer donor PTVT-BT without using any fused ring units. Both PTVT-V and PTVT-BT show obvious solution aggregation effects. Compared with PTVT-V, PTVT-BT shows much higher EQEEL (7 ×10-3) and hole mobility (1 ×10-2 cm2 V-1 s-1). Finally, the OPV cell based on PTVT-BT:eC9 demonstrates a PCE of 16.31% without using any additives, which is a very prominent result in polymer donors with low-cost characteristics. Based on PTVT-BT:BTA3, we obtained an indoor OPV cell with PCE of more than 27% (1000 lux). In addition, the tandem cell with PTVT-BT:BTA3:eC9 as rear sub-cell demonstrates an outstanding PCE of 18.49%. Importantly, the materials-only-cost (MOC) of PTVT-BT can be as low as 29.6 $/g. Therefore, the high-performance and low-cost polymer donor PTVT-BT reported in this work has great industrial application value.
Section snippets
Synthesis and characterizations of the PTV-derivatives
The TVT unit with the symmetric ester groups was retained in the new PTV-polymer, PTVT-BT, and PTVT-V was used as the control polymer donor to compare their photovoltaic properties. The number-averaged molar mass (Mn) PTVT-V used here is 3.13 × 104 g mol-1 with a dispersity of 2.70. The synthetic routes of PTVT-V and PTVT-BT are presented in Fig. 1a and the detailed synthetic procedures are provided in the Supporting Information (SI). PTVT-V and PTVT-BT were obtained by copolymerization with
Conclusion
In summary, an efficient PTV-derivative with very simple chemical structure, named PTVT-BT, was synthesized in only few steps from cheap raw materials. The MOC of PTVT-BT as low as 29.6 $/g. PTVT-BT possesses strong pre-aggregation behavior in solution state. Besides, compared to the control polymer PTVT-V, PTVT-BT demonstrates higher charge mobility (1 ×10-2 cm-2 V-1 s-1) and EQEEL (7 ×10-3), which enables the PTVT-BT has efficient charge generation, transport, and collection. As a result, the
CRediT authorship contribution statement
Pengqing Bi, Shaoqing Zhang and Jianhui Hou conceived the idea. Pengqing Bi, Jianqiu Wang, Zhong Zheng and Yong Cui carried out the device fabrications and characterizations. Junzhen Ren synthesized the polymers of PTVT-V and PTVT-BT. Pengqing Bi, Tao Zhang, and Jinzhao Qin conducted the morphology characterizations. Zhihao Chen and Xiaotao Hao conducted the TA characterizations. Mengyuan Gao and Long Ye calculated the Flory-Huggins interaction parameters. All authors discussed and commented on
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the financial support from National Natural Science Foundation of China (21835006), the National Key Research and Development Program of China (2019YFE0116700), and China Postdoctoral Science Foundation (2019M660799).
Pengqing Bi received his PhD degree from Shandong University in 2019. He currently is a postdoctoral researcher in Prof. Jianhui Hou’s group at Institute of Chemistry, Chinese Academy of Sciences (ICCAS). His current research interests are materials and physics of organic optoelectronic devices.
References (50)
- et al.
Joule
(2021) - et al.
Joule
(2021) - et al.
Joule
(2020) - et al.
Joule
(2021) - et al.
Polymer
(2020) - et al.
Nano Energy
(2018) - et al.
Science
(1995) - et al.
Chem. Rev.
(2009) - et al.
Nat. Rev. Mater.
(2018) - et al.
Chem. Soc. Rev.
(2019)
Science
Chin. J. Chem.
Nat. Energy
Adv. Mater.
Adv. Mater.
Adv. Energy Mater.
Adv. Mater.
Adv. Mater.
Angew. Chem. Int. Ed. Engl.
Chem. Rev.
Small
Nat. Commun.
Natl. Sci. Rev.
Angew. Chem. Int. Ed. Engl.
Nat. Commun.
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Pengqing Bi received his PhD degree from Shandong University in 2019. He currently is a postdoctoral researcher in Prof. Jianhui Hou’s group at Institute of Chemistry, Chinese Academy of Sciences (ICCAS). His current research interests are materials and physics of organic optoelectronic devices.
Junzhen Ren obtained his B.S. in Polymer Materials and Engineering from Ocean University of China in 2013, and is currently a PhD candidate under the supervision of Prof. Jianhui Hou at State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, University of Chinese Academy of Sciences, China. His research interests are the molecular design and synthesis of functional conjugated materials and device characterization for organic solar cells.
Shaoqing Zhang received her PhD degree in Organic Chemistry from University of Science and Technology Beijing (USTB) in 2017. She currently is an associate professor at school of chemistry and biological engineering in USTB, and her research focuses on molecular design, synthesis, and the application of highly-efficient organic photovoltaic materials.
Jianqiu Wang received his M.S degree in 2019 from Changchun University of Technology. Currently, he is pursuing Ph.D. under the supervision of Prof. Li Yongfang, Prof. Zhang Maojie and Prof. Jianhui Hou at Soochow university. His main research interest focuses on the device preparation and study of organic solar cells.
Zhihao Chen is currently a Ph.D. candidate under the supervision of Prof. Xiaotao Hao at the School of Physics, Shandong University, China. His main research interest is organic photovoltaics, transient absorption spectroscopy, and time-resolved fluorescence spectroscopy.
Mengyuan Gao earned her Bachelor degree in polymer materials & engineering from Taiyuan University of Technology, China, in July 2019. Currently, she is a Ph.D. candidate at the school of Materials Science & Engineering of Tianjin University under the supervision of Prof. Long Ye. Her research work focuses on understanding the mixing behaviors of conjugated polymer blends used in polymer solar cells and other types of electronics by applying polymer physics knowledge.
Yong Cui received his Ph.D. degree from University of Chinese Academy of Sciences in 2019 under the supervision of Prof. Jianhui Hou. He is currently an associate professor at Institute of Chemistry, Chinese Academy of Sciences (ICCAS). His research focuses on the study of materials and device engineering toward high-performance organic photovoltaic cells for versatile applications.
Tao Zhang obtained her M.S. degree from Anhui University of Science and Technology in 2020. She is currently a PhD student of Prof. Jianhui Hou at State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, University of Chinese Academy of Sciences, China. Her research focuses on the high-performance organic photovoltaic cells.
Jinzhao Qin received his BSc degree in department of polymer science and engineering from University of Science and Technology of China. Now he is a PHD candidate in Prof. Jianhui Hou’s group in Institute of Chemistry, Chinese Academy of Science (ICCAS). His current research focuses on organic photovoltaic device.
Zhong Zheng is now a professor working at University of Science & Technology Beijing (USTB), China. Prior to joining in USTB in 2022, he had worked at Institute of Chemistry,Chinese Academy of Sciences (ICCAS), National Center for Nanoscience and Technology (NCNST) and The University of Tokyo. His current research interests are tandem organic photovoltaics and Printed Electronics, etc.
Long Ye is a Professor at the School of Materials Science & Engineering of Tianjin University since October 2019. He received his Ph.D. degree from Institute of Chemistry, Chinese Academy of Sciences (Adviser: Prof. Jianhui Hou) in July 2015. From August 2015 to September 2019, he was a postdoctoral researcher and later promoted to research assistant professor in the same group headed by Prof. Harald Ade at the Department of Physics, North Carolina State University. His current interests include morphological and mechanical characterizations of semiconducting polymers and their blends in solar cells and transistors, and polymer physics of conjugated polymers.
Xiaotao Hao, a Fellow of Institute of Physics (FInstP) and a Fellow of Royal Society of Chemistry (FRSC), is now a professor working at School of Physics in Shandong University, China., He is also a key member of the State Key Laboratory of Crystal Materials. Prior to returning China in 2012, he had worked at several research institutions in Australia, Japan and Singapore. His current research interests are physics of organic optoelectronic materials and devices, time resolved fluorescence spectroscopy/microscopy, etc.
Jianhui Hou received his PhD degree in Physical Chemistry from ICCAS in 2006 (Adviser: Prof. Yongfang Li). Then he worked as a postdoctoral researcher at Prof. Yang Yang's group in University of California, Los Angeles (UCLA) from 2006 to 2008 and then as Director of Research of Solarmer Energy Inc. from 2008 to 2010. After that, he became a Full Professor at ICCAS in 2010 and an Adjunct Professor at USTB in 2012. His present research focuses on design, synthesis, and application of organic/polymer photovoltaic materials.