With the wide application of organic semiconductors (OSCs), researchers are now grappling with a new challenge: design and synthesize OSCs materials with specific functions to satisfy the requirements of high-performance semiconductor devices. Strain engineering is an effective method to improve the semiconductor material’s carrier mobility, which is fundamentally originated from the rearrangement of the atomic packing model of materials under mechanic stress. Here, we design and synthesize a new OSC material named AZO-BTBT-8 based on high-mobility benzo[b]benzo[4,5]thieno[2,3-d]thiophene (BTBT) as the semiconductor backbone. Octane is employed to increase molecular flexibility and solubility, and azobenzene at the other end of the BTBT backbone provides photoisomerization properties and structural balance. Notably, the AZO-BTBT-8 photoisomerization leads to lattice strain in thin-film devices, where exceptional device performance enhancement is realized. On this basis, a large-scale flexible organic field-effect transistor (OFET) device array is fabricated and realizes high-resolution UV imaging with reversible light response.

Ductile fracture is modeled by using a novel phase-field method of geometric type to avoid the use of the complicated discretization approaches for crack discontinuities. The plasticity model is defined by an over-nonlocal implicit gradient-enhanced framework, which is equivalent to the integral-type plasticity models and therefore strongly nonlocal. A modified phenomenological barrier function is used as the crack phase-field driving force by mainly considering the effects of the nonlocal plastic deformation under shear-dominated stress states. The ductile damage is assumed to solely affect the plastic energy stored capacity from the micro-mechanical perspective such that the proposed approach can be easily extended to more general loading conditions. The implementation of the proposed phase-field method is shown to be easily integrated into the commercial codes (e.g., ABAQUS) through the coupling use of several user interfaces. We present simulations of the shear band formation under axial compression and the ductile crack propagations in a single-edged notched plate, a slanted fracture specimen and a pure shear test specimen to elucidate the viability of the current nonlocal method. The numerical results adequately demonstrate that mesh dependency can be apparently alleviated if material softening occurs.

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