Study On The Piezophototronic Effect In GaSe Nanosheets

By mechanical stimuli,the photoelectric properties of semiconductor material can be influenced.This is called piezo-phototronic.It can interact force-electric-light,is highly desirable for applications in human-machine interfaces,micro electromechanical system,sensor and the self-driven system.There is a strong covalent bond in the two-dimensional material,and the layer and layer are only combined by the very weak van der Waals force.Thus,it has excellent mechanical properties.GaSe is a metal-monochalcogenide III–VI semiconductor with an interesting photoelectric effect,which is the ideal material for studying and applying piezo-phototronic effect.In this paper,we have studied the piezo-phototronic effect of GaSe.The main research contents are summarized as follows:First,we prepared GaSe nanosheets with wrinkles on PET substrate by adhesive tape.The relationship between photoluminescence and strain on GaSe was studied.It is found that the intensity and peak positions of the photoluminescence spectra change linearly with strain.Thus,it provides a way to probe the local strain.Secondly,two-terminal devices based on strained GaSe were fabricated on PDMS substrates.We demonstrate for the first time a giant piezo-phototronic response in GaSe.The out-of-plane local field due to band gap modulation drives the electrons(holes)to move towards the outer(inner)surface of the wrinkle,which enhanced the electron-hole pair generation and the related photocurrent.The conductivity and photocurrent increase linearly with strain when the strain is larger than 0.1%.When the bending deformation decreases by 0.2%,the conductance will be reduced by three times and the photocurrent will decrease by 4.5 times.Finally,we demonstrate the robust suitability of the GaSe nano-sheets for flexible optoelectronic-mechanical applications by measuring the resistance response during repeated bending of few layer GaSe.Manual bending of GaSe reliably enhances the photocurrent by more than a factor of 50 at room temperature.This giant and linear piezo-phototronic response combined with excellent stretchability suggests GaSe is a valuable material for flexible optoelectronic-mechanical applications.