Homogeneously Oriented Organic Single‐Crystalline Patterns Grown by Microspacing In‐Air Sublimation

Abstract

tial to develop a patterning technology to grow discrete organic crystals at desired positions. [6,7] However, due to the poor controllability of the crystallization process for the large-conjugated molecules, the prepared organic semiconductor crystals often suffer from random location, limited and ununiform crystal size, and disordered crystallographic orientation arrangement, which impede the subsequent device construction on them. [8][9][10][11][12][13] Compared with the preparation of continuous crystalline films of organic semiconductors, the essential points to grow discrete single-crystalline patterns are to align the crystallographic orientation among the patterns besides controlling their deposition locations. Because the intermolecular packing mode differs along different directions in the anisotropic single crystals, the carrier transporting channels have intrinsic dependence on the crystallographic orientation. [14] In the reported patterning strategies the solution-based techniques are most widely used, wherein photolithography is usually adopted to define the locations of the patterns assisted by self-assembled monolayers or surface microstructures. [2,[15][16][17][18][19][20] Such solution patterning is regarded to be facile to handle and low-cost; nevertheless, as an inherent drawback of solution-based techniques, the residual solvent molecules may act as vulnerabilities that affect the stability and ruin the electron conductance. [21,22] Another notable fact is that the solution method is not applicable to organic semiconductors with rigid structures because they are difficult to dissolve in most organic solvents. In contrast, the vaporbased techniques have been well-established in the commercialized organic light-emitting diodes manufacturing, wherein vacuum deposition assisted by fine metal masks has proved its feasibility in high resolution and high throughput. [23,24] Similarly, vapor deposition of organic single crystals also provides with high purity and high quality, without worries about solvent residue or the poor solubility of the rigid organic semiconductors in organic solvents. [25,26] Compared to the control over growth positions, to align the crystallographic orientation among the discrete anisotropic single crystal patterns is more intractable. Taking pentacene as an example, the mobility when the crystallographic long axis is parallel with the channel direction is about tenfold higher than Fabrication of single-crystalline organic semiconductor patterns is of key importance to enable practical applications. However due to the poor controllability on nucleation locations and the intrinsic anisotropic nature of singlecrystals, growth of single-crystal patterns with homogeneous orientation is a big challenge especially by the vapor method. Herein a vapor growth protocol to achieve patterned organic semiconductor single-crystals with high crystallinity and uniform crystallographic orientation is presented. The protocol relies on the recently invented microspacing in-air sublimation a...

Nanocrystal Array Engineering and Optoelectronic Applications of Organic Small-Molecule Semiconductors

“…The micro-spacing air sublimation method [ 71 ] can pattern small organic molecule single crystals, and the method of air sublimation can assist the solid substrate surface to perform wettability treatment [ 72 ], which can precisely control the growth position of an organic small-molecule semiconductor, so that the interconnected single crystal patterns have uniform crystal orientation, and higher crystallinities. Using, for example, 2,7-dioctyl[1]benzothieno[3,2-b] benzothiophene (C8-BTBT), this method can be used to prepare single crystal patterns of different shapes and sizes with uniform orientation.…”

“… ( a ) Micro-spacing air sublimation grown C8-BTBT crystal arrays. ( b ) Optical microscope (OM) image (top) and scanning electron microscope (SEM) image (bottom) of a C8-BTBT single crystal with different sizes and shapes [ 72 ]. Copyright© 2023 Wiley-VCH GmbH.…”