Study On Photodetector Based On Perovskite

Inorganic material research is generally high cost,long cycle and complex process in the field of optoelectronics.But in recent years,new photoelectronics functional materials(perovskites,PVK)which is newly discovered,have low cost,simple preparation and excellent photoelectric characteristics and which are represented by methylamino halide CH3NH3MX3(M = Pb,Sn,X = Cl,Br or I).Perovskite have attracted much attention due to the intrinsic properties of the materials,including high absorption coefficient,high carrier mobility,long carrier diffusion length,simple preparation process and low cost.Organic-inorganic halide perovskite is widely used in the field of optoelectronic,such as solar cells,transistors,and photo-detectors because of the outstanding photoelectric properties.Furthermore,perovskite has great advantages in achieving high performance,low power and low cost of photo-detectors,especially high response speed,high quantum efficiency and low dark current.But in the study of experiments,it is found that there are still many problems to be solved in the application of the device due to some properties of the material itself.We have done the following studies in response to the problems.Firstly,we prepared polycrystalline perovskite(CH3NH3Pb Ix Cl3-x)photo-detectors with a structure of Au/(CH3NH3Pb Ix Cl3-x /Au to research the temperature dependence of devices.The performance of perovskite photo-detectors at normal temperature was studied by a series of material characterization and electrical characterization.And the results showed the device had good performance.Then the effect of temperature(30-80 ?)on the performance of the device was studied and the charge transport mechanism were fitted by the properties of current–voltage(I–V).We found that only space charge limited conduction mechanism could fit the I-V curves under small external voltage(0.1–0.7 V)both under darkness and illumination.In addition,we found that the I-V curve decreases with the increase of temperature under dark condition and the I-V curve increases with the increase of temperature under light state.Theoretical analysis shows that the lattice vibration scattering plays the major role in the dark,leading to a decreased current as the temperature increases under the same external voltage,and an enlarged current increasing with the temperature is due to the leading role of the ionized impurity scattering.And at each temperature,the rising slope of the I–V curves decrease with the increase of voltageboth under dark and illumination.The values of on/off ratio,responsivity and detectivity increase with the measured temperature,which indicates that the polycrystalline perovskite photo-detector can work with better performance at high temperature.However,the stability in the dark gradually becomes weak as the temperature increases,especially at 60 ? and above.Besides,to investigate the stability problem of perovskite based photo-detector and to understand further the effect of PCBM on perovskite based electrical devices.We prepared two kinds of photo-detector(Au/CH3NH3 Pb Ix Cl3-x/Au and Au/CH3NH3 Pb Ix Cl3-x: PCBM(1.0wt%)/Au)and tested and analyzed contrastively the performance of the two kinds of photo-detector.Results showed that adding certain amount of PCBM in perovskite can suppress the movement of ions,thereby reducing the negative impact brought by the zero drift,and improve the stability of the detector performance.But at the same time,the conductivity change makes the light dark current ratio,detection capacity and detection the sensitivity decreased slightly when adding a certain amount of perovskite PCBM.Finally,on the basis of the above experiments,the effects of perovskite doped with different concentrations of PCBM on the performance of photo-detectors are studied in depth.Three photo-detectors with the structure of Au/CH3NH3 Pb I3/Au,Au/ CH3NH3 Pb I3:PCBM(0.01wt%)/Au and Au/ CH3NH3 Pb I3:PCBM(0.1wt%)/Au were prepared.The study found that PCBM still has the same conclusion as the previous experiment which PCBM has the effect of restraining the zero drift in the dark state.And at the same time,the dark current increases with the PCBM doping compared with the detector without PCBM,but the light current were no significant difference.Theoretical analysis indicated that the vacancies in perovskites are filled by PCBM doping which will release more captured electrons for transporting.