Intrinsically mechanical properties of polymeric semiconductor

Intrinsically flexible polymeric semiconductors are the most potential active candidates in flexible optoelectronics for their solution-processing ability, dynamic programmable mechanical property and excellent optoelectronic behaviour. Flexible optoelectronic, including stretchable film, flexible crystal, foldable and healable device, have recently received extensive concern in organic optoelectronics research but rarely effective and universal strategy to precisely systematically explore and evaluate the intrinsically mechanical property of polymeric semiconductor. Herein, we demonstrated a universal and convenient three-parameter model for nano-indentation test to systematically evaluate the intrinsically mechanical property of polymeric semiconductor. Significantly different to previous assumption about substrate-effect in nano-indentation test, we observed a critical testing depth (CTD) with a thickness ratio of < 10% to obtain an accurate mechanical parameters, such as hardness (H) and Young’s modulus (E_r). To systematically investigate the mechanical behaviour, three-parameter models are also introduced to obtain the proportion of elastic and plastic work. The entanglements of mainchain and side chain will provide an excellent flexibility and viscoelasticity of polymeric semiconductors. Therefore, it is emergent to construct an effective molecular design principle to obtain a viscoelastic rigid polymeric semiconductor for flexible optoelectronics, which presents slightly viscoelasticity and simultaneously further enhance stable optoelectronic property in solid states.