Strain-Engineering-Driven Photomechanical–Photoelectric Coupled Flexible Photodetector Based on Hexagonal Silicon Nanowire Films

Narrow band gap and photon-trapping structures of hexagonal silicon nanowire films were adopted for the photodetector (PD). To obtain higher carrier mobility and longer cutoff wavelengths, strain-engineering-induced wrinkled surface structures were utilized to overcome the band gap limitation and improve photoabsorption. The PDs were flexible, lightweight, tailorable, scalable, and semitransparent. Moreover, they could withstand 33% of tensile strain without structural damage, and the light resistor presents high sensitivity to tensile force and could be used as an optical force sensor. In the unstretched state, the responsivities at 375, 532, 1342, and 1550 nm reached a maximum of 41.72, 55.51, 3.41, and 6.38 mA·W–1, respectively, with fastest rise and fall times of 508 and 677 μs, respectively, and a high specific detectivity of 2.8 × 108 Jones (1550 nm at 5 V). Such fast photodetection from UV to NIR in silicon nanowire systems shows promising potential for flexible piezoelectric–photoelectric coupled detection applications.