Hybridizing Semiconductor Films With Graphene Towards Ultra-Flexible Image Sensors

There is an increasing demand in wearable electronics,especially for medical and security applications.Semiconductor films are compatible with the traditional complementary metal oxide semiconductor（CMOS）electronics and thereby widely used in image sensors.However,the brittle nature due to the crystal structure limits their practical applications in the future flexible image sensors and other optoelectronic devices.These brittle semiconductor films tend to crack at low mechanical strain and even lead to device failure.Herein,taking ZnSe/graphene hybrids as an example,this study attempts to demonstrate that hybridizing semiconductor films with highly flexible graphene is able to remarkably enhance the photoelectric properties and flexibility of semiconductor films-based image sensors.The semiconductor films based photodetectors were measured to have a low responsivity of 1.25×10^-5A/W.After bending under strain of 0.1%for 10 h,the ZnSe films based devices failed.This is because that the brittle ZnSe films act as both light absorption layer and channel,which limits the strain that the devices can bear.We fabricated flexible image sensors based on ZnSe film/graphene hybrids.The image sensors with a responsivity of 1.5×10⁶A/W could work normally under the large strain up to±20%.Also they make a stable performance under the strain of±0.2%after 10000 bending cycles or a bending duration of 3000 h.In semiconductor film/graphene hybrids-based device,high-mobility graphene provides a fast transport channel for the photo-generated carriers of semiconductor films via charge transfer mechanism,and thus semiconductor films only play a role in light absorption layer while graphene with much higher flexibility acts channel and determines the flexibility of the device.The variation of light absorption behavior for semiconductor film and charge transfer behavior at semiconductor film-graphene interface before and after bending are supposed to be ignored.As a result,the hybrids-based device is believed to work under the strain much larger than the value which leads to the variation of mechanical property in pure semiconductor films-based device.