Spatially Confined Face‐Selective Growth of Large‐Area 2D Organic Molecular Crystals in a Supramolecular Gel for Highly Efficient Flexible Photodetection

Abstract

2D organic molecular crystals (2DOMCs) are promising materials for the fabrication of high-performance optoelectronic devices. However, the growth of organic molecules into 2DOMCs remains a challenge because of the difficulties in controlling their self-assembly with a preferential orientation in solution-process crystallization. Herein, fullerene is chosen as a model molecule to develop a supramolecular gel crystallization approach to grow large-area 2DOMCs by controlling the perfect arrangement on the {220} crystal plane with the assistance of a gelated solvent. In this case, the gel networks provide tuneable confined spaces to control the crystallization kinetics toward the growth of dominant crystal faces by their inhibiting motions of solvent or solute molecules to enable the growth of perfect crystals at appropriate nucleation rates. As a result, a large-area fullerene 2DOMC is produced successfully and its corresponding device on a flexible substrate exhibits excellent bendable properties and ultra-high weak light detection ability (2.9 × 10 11 Jones) at a 10 V bias upon irradiation with 450 nm incident light. Moreover, its photoelectric properties remain unchanged after 200 cycles of bending at angles of 45, 90, and 180°. These results can be extended to the growth of other 2DOMCs for potentially fabricating advanced organic (opto)electronics.

Recent advances in supramolecular fullerene chemistry

“…469 Molecular gels have been used as spatially confined templates for the growth of C 60 crystals to obtain super-long crystalline C 60 fibers and large-area 2D crystals, which were utilized as photodetectors with high performance by Liu, Fang, and coworkers. 470,471 The dice-shaped Sc 3 N⊂C 80 3D crystals have been utilized as a support for the Pt-catalyzed methanol oxidation by Yang and coworkers. Catalyst performance was shown to be improved due to the larger surface area when compared with the cube shape crystals.…”

Solution-Processed Monolayer Molecular Crystals: From Precise Preparation to Advanced Applications

“…The geometrically confined 2D crystal growth method is found to be an effective technique for fabricating large-scale and ultrathin crystalline films. 67 In 2018, the Jiang group for the first time developed a gravity-assisted 2D spatial confinement method and realized the growth for centimeter-sized n-type CMUT (dicyanomethylene-substituted fused tetrathienoquinoid) MMCs. 34 As shown in Figure 7a, they take advantage of the different wettabilities of the CMUT/chlorobenzene solution on two different types of substrates: one is a hydrophobic substrate (octadecyltrichlorosilane (OTS) treated SiO 2 /Si), and the other is a hydrophilic substrate BCB treated SiO 2 /Si), to form ultrathin layers in the 2D space between the two substrates aided by the gravity of the top substrate, enabling the centimeter-sized CUMT MMC growth on the top hydrophilic substrate (Figure 7b).…”

“…The geometrically confined 2D crystal growth method is found to be an effective technique for fabricating large-scale and ultrathin crystalline films . In 2018, the Jiang group for the first time developed a gravity-assisted 2D spatial confinement method and realized the growth for centimeter-sized n-type CMUT (dicyanomethylene-substituted fused tetrathienoquinoid) MMCs .…”