(Invited) Innovative MOF-Based Strategies for Assembling Chromophores: Perspectives for Next-Generation Organic Electronics

In the realm of organic electronics, such as photovoltaics, photodetectors, and light-emitting devices, the integration of organic chromophores into solid-state assemblies and their connection with electrodes is crucial. A notable development in this area is the use of metal-organic frameworks (MOFs), also referred to as the MOF method [1], which has been gaining traction. This approach involves using organic chromophores like anthracene and other planar aromatics, including Hexa-peri-hexabenzocoronene (HBC), equipped with coupling units, to create ditopic linkers that connect with metal-oxo nodes in MOFs. In view of the challenges of integrating MOF powders into devices, recent advancements have led to the development of layer-by-layer methods yielding high-quality, monolithic MOF thin films [2]. These films offer exceptional optical qualities and show, in many cases, a reduced density of defects. MOFs' periodic structures enable the deliberate design of chromophore assemblies, impacting optical absorption through inter-molecular interactions. This design approach has facilitated the creation of structures like J-aggregates, initially simulated in silico and later realized experimentally [3]. Additionally, MOFs enable the realization of band-structure phenomena, such as indirect band gaps [4], and chiroptical effects, including circularly polarized light emission [5] and the helical sensitivity in photodetectors [6]. We've also explored lbl architectures for constructing heterostructures, useful in photon up-conversion applications. This involves leveraging MOFs' porous nature, as seen in the integration of C60 into SURMOF pores for applications like photoconductivity [7] and organic diodes [8]. Recent efforts have also focused on assembling non-centrosymmetric SURMOFs for nonlinear optical properties, demonstrating substantial second harmonic generation (SHG) activity [9]. Our presentation will showcase key instances of successfully incorporating organic chromophores into SURMOFs for device fabrication, emphasizing the synergy with theoretical models. Given the vast number (> 120,000) of known MOFs, a theoretical approach is essential to guide experimental efforts efficiently. References: [1] R. Haldar, L. Heinke, Ch. Wöll, Advanced Materials (2020), Adv. Mater., 2020, 32, 1905 [2] L. Heinke, Ch. Wöll, Adv. Mater., 2019, 31 (26), 1970184 [3] J. Liu, W. Zhou, J. Liu, I. Howard, G. Kilibarda, S. Schlabach, D. Coupry, M. Addicoat, S. Yoneda, Y. Tsuitsui, T. Sakurai, S. Seki, Z. Wang, P. Lindemann, E. Redel, Th. Heine, Ch. Wöll, Angew. Chemie Int. Ed. 54, 7441 (2015) [4] R. Haldar, A. Mazel, M. Krstic, Q. Zhang, M. Jakoby, I. A. Howard, B. S. Richards, N. Jung, D. Jacquemin, S. Diring, W. Wenzel, F. Odobel, Ch. Wöll, Nat. Comm., 10, 2048 (2019) [5] Y.H. Xiao, P. Weidler, S.S. Lin, C. Wöll, Z.G. Gu, J. Zhang, Adv. Functional Materials 32 (34), 2204289, (2022) [6] Y.-B. Tian, K. Tanaka, L.-M. Chang, C. Wöll, Z.-G. Gu and J. Zhang, Nano Letters 2023, 23 5794 [7] X. Liu, M. Kozlowska, T. Okkali, D. Wagner, T. Higashino, G. Brenner-Weiß, S. M. Marschner, Z. Fu, Q. Zhang, H. Imahori, S. Bräse, W. Wenzel, C. Wöll, L. Heinke, Angew.Chem.Int. Ed. 2019, 58, 9590 [8] A. Chandresh, X. Liu, Ch. Wöll, L. Heinke, Adv. Sci., 2021 , 8, 2001884 [9] A. Nefedov, R. Haldar, Z. Xu, H. Kühner, D. Hofmann, D. Goll, B. Sapotta, S. Hecht, M. Krstić, C. Rockstuhl, W. Wenzel, S. Bräse, P. Tegeder, E. Zojer, Ch. Wöll, Adv. Mat. 2103287 (2021)