Modulating Interfacial Self-Assembly and Molecular Arrangement via Functionalized Polymers for Organic Optoelectronics

ABSTRACT BODY:
Organic semiconductors are lightweight, flexible, and versatile, making them a promising next-generation material for a variety of electronic applications, including light-emitting diodes, thin-film transistors, energy harvesting, photodetectors, and more. Recently, non-fullerene acceptor materials, especially Y6, have attracted much attention in the field of organic photovoltaics due to their excellent optoelectronic properties and highly reproducible performance with PM6 polymer donors.[1] Nevertheless, high-efficiency PM6:Y6 active layer-based organic optoelectronic devices are unavoidably fabricated in chloroform, which has a relatively low boiling point, which limits the adoption of large-area processes and a variety of applications. To solve this problem, we have succeeded in forming PM6:Y6 heterojunctions based on chlorobenzene, which has a relatively low boiling point, and introducing a molecular orientation favorable for charge transport by introducing a dry printing process. [2,3] Using the functionalized polymer substrate, we succeeded in fabricating large areas and verified a high reproducibility range via simulation based on the wetting coefficient of the surface. In addition, the process not only controlled the interfaces, but also controlled the crystallinity and molecular arrangement of the active layer through additional A-D-A structured small molecule materials, resulting in highly reproducible active layer formation.[4] The electron transport layer being studied, n-type perylene diimide (NPDI), is widely utilized as an interlayer between the active layer and the cathode in optoelectronic devices due to its work function tunability and excellent charge mobility. However, as a two-dimensional planar small molecule, NPDI is highly self-assembling, leading to undesirable molecular aggregation, which can lead to inadequate coverage of the entire surface of the active layer, resulting in high leakage current. To overcome this, a dry printing process was introduced to form a uniform and coherent arrangement of NPDI layers for the first time. [5] In particular, an alcohol-based solvent, 2,2,2-trifluoroethanol, was used to successfully control the film formation rate, and a functionalized polymer release mold was employed. The coherent arrangement of NPDI layer significantly increased the charge mobility and effectively suppressed the trap density at the interface. Furthermore, the modification of the interfacial morphology and defect suppression in a coherent arrangement of NPDI-based organic photodetector effectively suppressed the dark current and significantly enhanced the detectivity. Furthermore, we applied this dry printing process to flexible organic optoelectronic devices, demonstrating the feasibility of effective interfacial engineering on flexible substrates.

[1] R. Yu, G. Wu, & Z. A. Tan, J. Energy Chem., 2021, 61, 29-46.
[2] M. S. Kim, W. Jang, T. Q. Nguyen, D. H. Wang, Adv. Funct. Mater., 2021, 31(38), 2170278.
[3] J. Lim, M. S. Kim, W. Jang, D. H. Wang, ACS Sustain. Chem. Eng.,2023, 11, 625–637.
[4] J. Lim, N. Lee, W. Jang, B. Bae, S. Lee, W. Han, J. K., Park, D. H. Wang, Chem. Eng. J, 2024, 495, 153417.
[5] J. Lim, W. Jang, Z. Yang, D. H. Wang, J. Mater. Chem. A, 2024, 12, 7765-7776.