Large electric piezoresistance of the flexible molecular semiconductive crystal Q(TCNQ)2 during bending

Abstract

Elastic and plastic molecular crystals that exhibit electrical conductivity have attracted much attention. Flexible molecular semiconductors exhibiting significant piezoresistivity can be utilized in mechanical sensors in which the application of silicon-based semiconductors is difficult. In this study, we prepared a simple stress–strain measuring apparatus that can be combined with electric measuring instruments. The electric resistivity of the organic semiconductive crystal of Q(TCNQ)₂ (Q⁺ = quinolinium) was measured during the stress–strain test. A large increase in resistivity was observed during the bending of the Q(TCNQ)₂ crystal. The coefficient of the resistivity change against strain was much larger than that of the general strain gauge comprising metallic alloys, where the elastic limit was considerably larger than that of the strain gauge fabricated using silicon-based semiconductors. The large resistivity change was described using a tight-binding model with simple material mechanics.