The Fabrication And Properties Of ZnO Nanorods Based Self-Powered UV Detectors

Ultraviolet(UV)detection technology is widely used in many fields,such as space communication,pollution monitoring,missile plume detection and even biomedical applications.Compared to commercial photomultiplier and Si basde UV photodetectors,the third generation wide bandgap semiconductor based UV photodetectors have received extensive attention owing to the realization of UV detection function without additional optical filter and cooling system.Among various wide bandgap semiconductor materials,1D ZnO nanostructure is regarded as one of the most important nanomaterials for UV photodetection,benefiting from its unique characteristics,such as stable physical and chemical properties,strong radiation hardness,large surface area to volume ratio,high electron mobility,process simplicity and environment-friendly.However,lots of traditional UV detectors need a certain applied potential in order to obtain reasonable detectivity,which makes the overall circuitry heavy and uneconomical in the current energy situation.As a result,a self-powered photodetector has drawn great attention,which can be used in many harsh environments without external power.Although some progress has been made in the study of nanostructure ZnO based UV detectors,there are still lots of challenges:the structure and preparation process of the device is too complex;many detectors need a certain applied potential in order to work,which wastes energy;the performance of the device is unstable;Especially it is hard to obtain both high sensitivity and fast response in the bending condition.To obtain high stability and high performance self-powered UV detectors,we prepared high quality ZnO nanorods by hydrothermal method;assembling with a novel quasi-solid electrolyte or hole transport layer,we obtained quisi-solid flexible type and solid flexible type self-powered UV detector;by increasing the contact interface between ZnO nanorods and the electrolyte or hole transport layer,the detector shows high response and the transportation of the carriers was enhanced.The specific research contents are as follows:1.Vertically grown ZnO nanorods were successfully prepared on glass substrates by a simple hydrothermal method.A photoelectrochemical cell(PECC)type self-powered UV photodetector was obtained by assembling ZnO NRs with an iodine free quasi-solid electrolyte.The dependences of photocurrent on KI and PEO were investigated in detail and the working principle of the device was analyzed.It is found that the photocurrent increases first and then decreases with the increasing of the content of KI and PEO,mainly due to the complexing reaction between the electrolytes.The optimum photocurrent is 4×10-4 A for the sample containing 0.03 g KI and 0.2 g PEO,the corresponding high responsivity is 2.33 A/W and the rise and decay time are 0.09 s and 0.31 s,respectively.The electrolyte is amorphous in this case owing to the complete complexing reaction,which enhances the contact interface between ZnO nanorods and electrolyte.As a result,the electron channels are increased and electron transportation is enhanced.2.We successfully prepared the ZnO NRs on ITO coated PET substrate by a facile hydrothermal method.A flexible,stable,low-cost and self-powered UV photodetector was fabricated based on ZnO NRs and a novel iodine-free quasi solid-state electrolyte,which showed fast and high response to UV light at 0 V.The rise and decay time are 0.03 s and 0.13 s,respectively.The responsivity is 50.5 mA/W The stain-induced piezopotential on the performance of the ZnO NRs/electrolyte was investigated in detail.The photocurrent increases step by step with the increasing of the downward angles,decreases with the increasing of the upward angles.About 63%enhanced responsivity could be achived when the downward angles up to 60°The enhancement mechanism is attributed to the piezo-phototronic effect within the ZnO.3.We successfully prepared the ZnO NRs on ITO coated PET substrate by a facile hydrothermal method.The heterojunction self-powered UV detectors were obtained by assembling with the novel hole transport layer R01.The device has fast response at 0 V,and the rise time and decay time are 0.05 and 0.12 s,respectively.Due to the effective contact between ZnO nanorods and R01,the responsibility is 90.9 mA/W.The performance of device in flax state,natural state and revertant state is good,and showed little difference.The device has a certain thermal stability,and the device still has a good UV detection performance at the test temperature of 80 ℃.