| Organic-inorganic composite perovskites have recently attracted intense interests for soler cells application due to their excellent photovoltaic and photoelectric properties,such as strong light absorption,low electron-hole pair binding energy,long carrier diffusion length,and preparation process simple and low cost.From 2009,Organic-inorganic composite perovskites first as visible light sensitizers have been considered for photovoltaic cells by Miyasaka et al.By now,the battery conversion efficiency has increased from 3.8%to 23.2%.The rapid advancement of organic-inorganic composite perovskite materials in the field of solar cells have also spawned its applications in other optoelectronic devices,such as light-emitting diodes?LEDs?,lasers,and photodetectors,especially in the field of photodetectors.So far,organic-inorganic composite perovskite based photodetectors had three main structures:photoconductive,photodiode,and phototransistor.These structures didn't in line with the low power consumption trends in the semiconductor industry due to their relatively large dark currents.Based on mentioned above,a perovskite photodetector with a metal-oxide-semiconductor?MOS?structure was fabricated,in which the leakage current of MOS was regard as the output current,and it greatly reduces the dark state power consumption.The effects of iodine ions in perovskite,oxide layer thickness and different oxide layer materials on the characteristics of perovskite based MOS structure photodetectors were studied.This article mainly includes:1.A thickness of 300 nm silicon dioxide?SiO2?was prepared on the surface of a silicon?Si?substrate by thermal oxidation process.A thickness of 300 nm perovskite was prepared on the surface of SiO2 by one-step solution methed.The magnetron sputtering process was used in the surface of perovskite and the lower surface of Si substrate to prepare a thickness of150 nm electrode Au and electrode Al.And finally an Al/Si-SiO2-perovskite-Au structure photodetector was formed.The prepared polycrystalline perovskite films were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,photoluminescence?PL?,ultraviolet-visible absorption?UV?,and ray photoelectron spectroscopy?XPS?.2.Capacitance-voltage?C-V?,current-voltage?I-V?and current-time?I-t?tests were performed on the prepared perovskite MOS structure detector.According to the test results,the detector had a dark state power consumption of 0.2×10-10 W,a responsivity of 1×10-4 A/W,an opening ratio of 325,and a detection sensitivity of 3.16×109 Jones at a light intensity of 10 mW/cm2 with a bias voltage of 1 V.At the same time,the C-V test indicated that the prepared perovskite was an N-type semiconductor,and the light intensity and test frequency had a great influence on the capacitance.In the dark state,the C-V curve shown a hysteresis attributed to the forward scan and the reverse scan didn't coincide.However,the hysteresis disappears after illumination.According to the C-V curve,the carrier concentration in the perovskite was 1.91×1015 cm-3 in the dark state,and was increased to2.87×1015 cm-3 at the light intensity of 10 mW/cm2.The I-V test shown that the transport mechanisms of the detector were dominated by the ohmic mechanism and the ion conduction mechanism,and the I-V curve also exhibited hysteresis in the dark state,and the hysteresis disappeared after illumination.The I-t test shown that the detector had a longer response time.3.The effect of iodide ions in the perovskite on the detector was studied.After iodine doping,the detector had a dark state power consumption of 1×10-10 W,a responsivity of 1.6×10-3A/W,an opening ratio of 1000,and a detection sensitivity of 1.1×1010 Jones at a light intensity of 10 mW/cm2 with a bias voltage of 1 V.At the same time,the experimental results shown that C-V and I-V hysteresis was enhanced after iodine doping.Based on experiment,a theoretical model of hysteresis was proposed.4.The effect of different SiO2 thickness on the detector was studied.It is shown that the detector had a dark state power consumption of 1×10-10 W,a responsivity of 4.7×10-4 A/W,an opening ratio of 300,and a detection sensitivity of 3.3×109 Jones at a light density of 10mW/cm2 with a bias voltage of 1 V when the thickness of SiO2 is 200 nm.At the same time,I-V test shown that the transport mechanism of the detector was not only the ohmic mechanism and the ion conduction mechanism,but also the Frenkel-Poole emission mechanism.The I-t test shown that the response time of the detector was significantly reduced when the thickness of SiO2 was 200 nm.When the thickness of SiO2 is 500 nm,the light current of the detector was smaller than that of the dark state.5.The effect of different oxide layer materials on the detector was studied.It was found that when Alumina oxide?Al2O3?was substituted for SiO2,the detector had a dark state power consumption of 5×10-10 W,a responsivity of 2.4×10-3 A/W,an opening ratio of 300,and a detection sensitivity of 1.5×1010 Jones at a light intensity of 10 mW/cm2 with a bias voltage of 1 V.At the same time,the I-V test shown that the transport mechanism of the Al2O3 oxide based detector was dominated by the ohmic mechanism,the ion conduction mechanism and the Schottky emission mechanism.And the thinner Al2O3 thickness could effectively reduce the response time of the detector.When Hafnium oxide?HfO2?was substituted for SiO2,there was no significant change in the light current and dark current of the detector. |
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