Study On Photoelectric Properties Of One-Dimensional CH₃NH₃PbI₃ Perovskite Micro/Nanowire-based Device

CH₃NH₃PbI₃organic-inorganic hybrid perovskite material has become a highly promising new photovoltaic materials due to its outstanding photovoltaic conversion efficiency and low fabrication cost.However,the common low temperature synthesis process is easy to lead to rich trap states inside the material,which will affect the photoelectric properties and stability of the material to a certain extent.In order to improve device performance,it is very important to explore how material trap states affect device performance.To solve this problem,many scholars have proposed different mechanisms to explain,such as conductive filaments,non-radiative recombination,charge capture,charge scattering and ion migration theories.However,the actual physical mechanism of trap state affecting material properties is still controversial.To address this issue,one-dimensional nanodevices is an ideal choice for systematically exploring the physical mechanism of the material properties because of their simple structure and easy controllability.In this paper,one-dimensional CH₃NH₃PbI₃micro/nanowire dual-electrode device was constructed,and the photoelectric performance of the device was precisely controlled by using external signals such as light sources,heat sources,and voltage sources.The internal origins of them are identified in depth,and these phenomena can be applied for multi-resistance state light storage,negative photo-thermal storage,self-powered photoelectric detection,and logic operation.The specific research contents and results of this thesis are as follows:1.CH₃NH₃PbI₃perovskite micro/nanowires were synthesized by two-step solution annealing method,and Ag/CH₃NH₃PbI₃/Ag（MSM）one-dimensional double electrode structure was constructed.Under strong light excitation,the device exhibits a symmetric clockwise hysteresis loop,while after being controlled by strong light and+10 V,the I-V curve shows an asymmetric clockwise crossing loop with a negative differential resistance（NDR）effect at the positive end.Under weak light and 5 V conditions,the controlled device exhibits excellent non-volatile photo-resistive memory characteristics.Conversely,after being controlled by strong light and-10 V,the I-V curve shows the opposite counterclockwise crossing loop,and the corresponding NDR effect occurs at the negative end.The photoresistive memory characteristics under weak light and 5 V conditions are also completely opposite.Under weak light and small bias voltage,the device exhibits novel multi-resistance state characteristics after being controlled,and can function as a multi-resistance state logic optical storage device.The internal mechanism of this property can be attributed to the asymmetric interface barrier generated by the interface oxidation-reduction reaction under strong light and large bias voltage.This precisely controllable multi-resistance state optical storage device has certain potential applications in multifunctional optoelectronic fields.2.Ag/CH₃NH₃PbI₃/C（MSC）asymmetric dual-electrode device based on single CH₃NH₃PbI₃micro/nanowire was constructed.Under strong light irradiation,the cyclic I-V curve of the device exhibits significant hysteresis behavior and excellent optical storage performance:at a reading voltage of 0.1 V,the memory window can reach about 40,at a reading voltage of-0.16 V,the memory window is about 2.5.The device also exhibits a lag effect in dark.When setting the voltage and visible light source as input A and B,and the current as output C,the device can perform simple"0"and"1"logic"OR"operations.After regulated by+10 V and-10V,the device showed completely different hysteresis effects and storage characteristics.When irradiated with continuous spectral light,the optical response peaks of the positive and negative interfaces also show obvious differences.The internal mechanism can be attributed to the oxidation/reduction of at the Ag electrode interface under the regulation of+10 V/-10 V bias,as well as the trapping/releasing of holes by the traps at the C electrode interface.This device with memory effect and logic operation has certain application potential in the field of integrated sensing and computing devices.3.Ag/CH₃NH₃PbI₃/C（MSC）asymmetric double-electrode device based on single micro/nanowire was constructed.After being encapsulated with polydimethylsiloxane（PDMS）,the device exhibited good self-powered photodetective performance under visible light irradiation:At low bias voltage,the maximum on/off ratio reached 10³,and the response and decay time were 0.2 s and0.3 s,respectively,the rectification ratio reached 1.8.At 0 V bias,the maximum photogenerated current and voltage was about 3.8 n A and 0.2 V,respectively.The electric transport characteristics under different light power intensities and biases were measured,and it was found that the rectification ratio was positively correlated with the light intensity while negatively correlated with the voltage.When the Ag electrode and C electrode interfaces was respectively irradiated under visible light,the photogenerated voltage was 0.15 V and 0.4 n A,while the photogenerated current was 0.08 V and 0.6 n A,respectively,exhibiting completely different characteristics.This self-powered photodetector can provide power for wearable devices.The self-powered characteristic of the device can be attributed to the asymmetric interface effect induced by different electrodes and the stronger interface photovoltaic effect at the perovskite/Ag interface.This simple,small-volume,and self-powered asymmetric device has certain potential for applications in the field of self-powered optoelectronics and wearable technology.4.Ag/CH₃NH₃PbI₃/Ag（MSM）double-electrode device based on a single-micro/nanowire was constructed.Under visible light and sub-bandgap light,the device exhibits an anomalous negative photoconductivity（NPC）effect after annealing at 160℃,and the most obvious effect occurred under 650 nm light.The device after annealing at high temperature can also produce a positive thermal resistive effect similar to the negative photoconductivity effect under low-temperature.When written with sub-bandgap 650 nm light and low-temperature,erased with high bias voltage and 365 nm super-bandgap light,the device can achieve multi-resistance state storage property,but also execute logical"OR"operations.The negative photoelectric storage effect and positive thermal resistive effect of the device can be attributed to that the holes escaped from the bulk trap generated by annealing under strong light and heat excitation.This multifunctional device integrated with negative photoelectric storage,thermal storage performance,and logical operation has certain potential for applications in new optoelectronic sensing,storage,and computation integrated field.