| Perovskite(CH3NH3Pb I3)is a new type of organic-inorganic hybrid photoelectric material,which has the advantages and disadvantages of both organic and inorganic.Compared with inorganic materials,it is easy to prepare,simple in process and low in cost.Compared with organic materials,it has higher carrier mobility and light absorption capacity.The disadvantages of perovskite are unstable chemical properties,easy to decompose in water and heat.Perovskite has been widely used in various fields,especially in the photoelectric conversion characteristics.The application of solar cells is the most well-known,and the efficiency of the preparation of solar cells increased from 3.8%in 2009 to 25.5%at present.Titanium oxide(Ti O2)and zinc oxide(Zn O)are often used as electron transport layers in perovskite solar cells.The heterojunctions they form with perovskites have been widely studied.Gallium oxide(Ga2O3)has attracted researchers'attention in the field of wide band gap semiconductors due to its excellent electrical conductivity and light emitting characteristics.Ga2O3is similar to Zn O in that the conduction band is very close to that of perovskite.Theoretically,the barrier is smaller than that of other materials when forming a heterojunction,which is conducive to electron transport and improves device performance.At present,the heterojunction formed by Ga2O3and perovskite has not been widely studied.This paper will prepare the heterojunction formed by Zn O and Ga2O3with perovskite to study its characteristics,and calculate and analyze the performance parameters of heterojunction photodetectors.This article mainly includes:1.Gallium oxide with thickness of 6 nm,12 nm,18 nm and 24 nm were prepared by magnetron sputtering(PVD)on the heavily doped silica(Si O2)at 500 nm.Gallium oxide with thickness of 100 nm,300 nm and 500 nm were prepared by atomic layer deposition(ALD)at Si O2.And zinc oxide with thickness of 5 nm,10 nm,100 nm,300 nm and 500nm were prepared by atomic layer deposition(ALD)at Si O2.Then perovskite with thickness of 300 nm was prepared on the surface of gallium oxide and zinc oxide by one-step solution method.160 nm thick aluminum(Al)and gold(Au)electrodes were prepared on the surface of Si O2and perovskite by magnetron sputtering.Finally,Al/Si O2/metal oxide/CH3NH3Pb I3/Au devices were formed.The gallium oxide,zinc oxide and perovskite films were characterized by SEM,ellipsometry,XRD,PL,UV and XPS.2.The prepared devices were tested for current-voltage(I-V)and current-time(I-t).The influence of electrical properties of heterojunctions formed by metal oxides with different thicknesses and perovskites was studied.According to the I-V test results and related calculations,it was found that in the Al/Ga2O3/CH3NH3Pb I3/Au structure,when the thickness of gallium oxide were 12 nm,18 nm,24 nm,the carrier transport mechanism was Schottky emission mechanism.When the thickness were 100nm,300 nm,500 nm,the main transport mechanism of the carrier became the ohmic mechanism.With the same transport mechanism and other conditions being consistent,the increase in gallium oxide thickness would make the current smaller.For the Zn O-based device structure,the carrier transport mechanism was the Schottky emission mechanism.At the same voltage,the current decreased as the thickness of the zinc oxide increased.3.The effects of different light intensities on the electrical characteristics of the device were studied.The light intensities were 10 m W/cm2,7.5 m W/cm2,5 m W/cm2,and dark conditions.Experiments were performed on more than 20 samples with different light intensities.Tests have shown that all devices showed that as the light intensity increases,the photogenerated current would increase,indicating that the increase in light intensity would cause the perovskite as a light absorbing layer to generate more photogenerated carriers.The experimental results also showed that the increase in the thickness of the metal oxide would hinder the device's response to light intensity,and the annealing process would increase the device's response to light intensity.4.The influence of metal oxide annealing on the electrical characteristics of the device was investigated.Hysteresis of the I-V image of the device was increase after the gallium oxide was annealed,indicating that the mobile ions in the gallium oxide thin film layer increased after annealing.The experimental results showed that the opening voltage of the heterojunction after the metal oxide was annealed was increased,which indicated that the electronic activation energy of the metal oxide was increased after the annealing.The metal oxide annealing process would affect the performance of the device as a photodetector.Under the same conditions,the dark-state power of the heterojunction photodetectors after annealing of metal oxides were generally lower than that of unannealed,and the ratio of open to light was generally greater than that of unannealed.Metal oxide annealing would reduce the photoelectric conversion rate of the detector,but it would reduce the power consumption of the detector,resulting in a significant increase in the detection capability of the detector.In general,the performance of the device as a photodetector would be greatly improved after annealing the metal oxide of the device.5.The experiment found that when the zinc oxide layer is 5 nm and 10 nm,the sample would self-power,that is,when the voltage was zero,the sample was connected to a closed circuit and light was applied,and a current would be generated in the circuit when there was no external power supply.The light-on ratio was up to 1198,and the detection capability of the detector was very significant.It is hoped that a self-powered detector can be prepared. |
PDF Full Text Request