van der Waals Epitaxy of Organic Semiconductor Thin Films on Atomically Thin Graphene Templates for Optoelectronic Applications

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Nguyen Ngan Nguyen - , Chair of Molecular Functional Materials (cfaed) (Author)
  • Hansol Lee - , Pohang University of Science and Technology, Gachon University (Author)
  • Hyo Chan Lee - , Myongji University (Author)
  • Kilwon Cho - , Pohang University of Science and Technology (Author)

Abstract

ConspectusOrganic semiconductors (OSCs) offer unique advantages with respect to mechanical flexibility, low-cost processing, and tunable properties. The optical and electrical properties of devices based on OSCs can be greatly improved when an OSC is coupled with graphene in a certain manner. Our research group has focused on using graphene as a growth template for OSCs and incorporating such high-quality heterostructures into optoelectronic devices. The idea is that graphene’s atomically flat surface with a uniform sp2 carbon network can serve as a perfect quasi-epitaxial template for the growth of OSCs. In addition, OSC-graphene heterostructures benefit from graphene’s unique characteristics, such as its high charge-carrier mobility, excellent optical transparency, and fascinating mechanical durability and flexibility.However, we have often found that OSC molecules assemble on graphene in unpredictable manners that vary from batch to batch. From observations of numerous research systems, we elucidated the mechanism underlying such poor repeatability and set out a framework to actually control the template effect of graphene on OSCs. In this Account, we not only present our scientific findings in this spectrum of areas but also convey our research scheme to the readers so that similar heterostructure complexes can be systematically studied.We began with experiments showing that the growth of OSCs on a graphene surface was driven by van der Waals interactions and is therefore sensitive to the cleanliness of the graphene surface. Nonetheless, we noted that, even on similarly clean graphene surfaces, the OSC thin film still varied with the underlying substrate. Thanks to the graphene-transfer method and in situ gating methods that we developed, we discovered that the decisive parameter for molecule-graphene interaction (and, hence, for the growth of OSCs on graphene) is the charge density in the graphene. Thus, to prepare a graphene template for high-quality graphene-OSC heterostructures, we controlled the charge density in the graphene to minimize the molecule-graphene interaction. Moreover, the possible charge transfer between OSC molecules and graphene, which induces additional molecule-graphene interactions, should also be taken into account. Eventually, we demonstrated a wide range of optoelectronic applications that benefitted from high-quality OSC-graphene heterostructures fabricated using our proof-of-concept systems.

Details

Original languageEnglish
Pages (from-to)673-684
Number of pages12
JournalAccounts of chemical research
Volume55
Issue number5
Publication statusPublished - 1 Mar 2022
Peer-reviewedYes

External IDs

PubMed 35142485
WOS 000768217100001
Mendeley 6622e641-8001-39c7-982a-83efbdae4275

Keywords

Research priority areas of TU Dresden

DFG Classification of Subject Areas according to Review Boards

ASJC Scopus subject areas