Crystal clear

Controlling the growth of single-crystal organic semiconductors has implications for flexible large-area electronic devices

Credit: © 2006 Nature

The flexibility, low cost and large-scale production of organic single-crystal semiconductors makes them practical alternatives to their inorganic counterparts in the electronics industry for fabricating flat-panel displays, plastic integrated circuits and photovoltaics. However, the performance of organic semiconductor arrays made by conventional methods is limited by electrical interference or 'cross-talk' between neighbouring devices.

Now, Zhenan Bao and colleagues¹ from Stanford University and the University of California, Los Angeles, USA have used a combination of contact printing and vapour growth to selectively deposit single crystals of organic molecules directly between the source and drain electrodes of transistors on both rigid and flexible substrates. Initially, films of hydrophobic organic molecules (octadecyltriethoxysilane) were patterned on either silicon/silicon dioxide or flexible polymer substrates. Vapour deposition of organic semiconductors including both p-type (rubrene) and n-type (C₆₀) materials resulted in single-crystal growth selectively on the patterned films. Crystal growth occurred quickly across large areas and the electrical characteristics of 14×14 arrays of rubrene transistors were comparable with conventional amorphous silicon and organic thin-film transistors.

The ability to control the spatial location and density of molecular single crystals is a major advance for their use as organic semiconductors for large-area flexible electronics.