2D Transition Metal Dichalcogenide with Increased Entropy for Piezoelectric Electronics.

Piezoelectricity in 2D transition metal dichalcogenides (TMDs) has attracted considerable interest because of their excellent flexibility and high piezoelectric coefficient compared to conventional piezoelectric bulk materials. However, the ability to regulate the piezoelectric properties is limited because the entropy is constant for certain binary TMDs other than multielement ones. Herein, in order to increase the entropy, a ternary TMDs alloy, Mo 1- x W x S 2 , with different W concentrations, is synthesized. The W concentration in the Mo 1- x W x S 2 alloy can be controlled precisely in the low-supersaturation synthesis and the entropy can be tuned accordingly. The Mo 0.46 W 0.54 S 2 alloy (x = 0.54) has the highest configurational entropy and best piezoelectric properties, such as a piezoelectric coefficient of 4.22 pm V -1 and a piezoelectric output current of 150 pA at 0.24% strain. More importantly, it can be combined into a larger package to increase the output current to 600 pA to cater to self-powered applications. Combining with excellent mechanical durability, a mechanical sensor based on the Mo 0.46 W 0.54 S 2 alloy is demonstrated for real-time health monitoring.