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Various epitaxial mechanisms have been proposed to control the growth orientation of vapor-deposited nanowires, yet the required lattice matching between target nanowires and supporting substrates limits their applicability. In this work, a versatile hot stamping protocol for fabricating parallel hydrophobic nanogrooves on flexible polymer films (e.g., polyimide (PI), polyethylene naphthalate (PEN), polydimethylsiloxane (PDMS)) is proposed. More interestingly, various organic small molecules, including several metal phthalocyanines (MPc, M = Cu, Zn, Fe, Ni, Co), 9,10-bis(phenylethynyl) anthracene (BPEA), 9,10-diphenylanthracene (DPA), and tris-(8-hydroxyquinoline)aluminium (Alq 3 ), are directly assembled into horizontally-oriented nanowires along the hot-stamped nanogrooves on a flexible PI film, thereby breaking the lattice-matching limitation for oriented nanowire growth. These submillimeter-long horizontally oriented nanowires can be integrated into flexible photodetectors directly on their growth film, eliminating the need for laborious post-growth transfer and alignment steps and the associated structural damage and contamination. Consequently, the in situ integrated flexible photodetector made of aligned CuPc nanowires maintains a stable and fast photoresponse to a spectrum in the region of 405-980 nm even when the detector is bent to a radius of curvature of 2.5 mm and 1000 times. This work will open new opportunities to develop in situ integrated flexible devices based on organic crystalline nanowires for practical applications.

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Large-scale on-chip integration of organic nanowire-based devices requires the deterministic assembly of organic small molecules into highly-aligned nanowires. In this work, phthalocyanine molecules are self-assembled into horizontally-aligned nanowires after generating parallel hydrophobic nanogrooves on a sapphire surface. In contrast to previous self-oriented inorganic nanowires, these molecular nanowires are separated from their supporting sapphire by an ultrathin amorphous layer, indicating a complete elimination of lattice matching between nanowires and substrates. Therefore, small molecules beyond phthalocyanines hold promise to form aligned nanowires using this graphoepitaxial self-assembly strategy. The excellent alignment and high crystallinity of these nanowires enable the desired in-situ integration of nanowire-based devices without additional postgrowth processing steps. As a proof of concept, self-oriented CuPc nanowires are integrated into photodetector arrays directly on their growth substrate after electrode arrays are transferred onto the nanowires. Compared to previous CuPc photodetectors constructed using other approaches, these detectors exhibit a faster response to the spectrum in the 488-780 nm range (rise and fall times are 0.05-0.43 s and 0.38-2.34 s, respectively) while offering comparable detectivities (2.49 × 10 10 Jones on average). This graphoepitaxial self-assembly offers new opportunities for the aligned growth of organic crystalline nanowires and their large-scale in-situ integration into functional devices.

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