Horizontally-Oriented Growth of Organic Crystalline Nanowires on Polymer Films for In-Situ Flexible Photodetectors with Vis-NIR Response and High Bending Stability

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.