Chinese and U.S. researchers have teamed up to synthesize and study the first organic single-crystal nanoribbon to feature a p-n heterojunction (J. Am. Chem. Soc., DOI: 10.1021/ja102779x). Most microelectronic devices depend on small crystals of silicon or other semiconductors that pair a tiny positive (p-type) charge-transporting region of the material with a negative (n-type) region. The abrupt interface between the two regions, known as a p-n junction, is critical to device performance. These junctions are typically formed by selectively modifying each side of the interface with different chemical dopants. Organic semiconductor devices, such as the polymer solar cells featured on the cover of this issue of C&EN, are starting to become more common, but their numbers are limited because conventional methods for forming inorganic p-n junctions can’t be readily applied to organic compounds. To sidestep the problem, Alejandro L. Briseno of the University of Massachusetts, Amherst; Wenping Hu of the Chinese Academy of Sciences; and coworkers formed single-crystal nanoribbons by selectively crystallizing copper hexadecafluorophthalocyanine (n-type material) on copper phthalocyanine (p-type material). The team then demonstrated the nanoribbons’ utility by incorporating them into transistors and solar cells.