Preparation And Photoelectric Properties Of Perovskite Single Crystal

ABX₃ perovskite materials have been developed for solar cells,light-emitting diodes,field-effect transistors,and photodetectors due to their excellent photoelectric properties.Perovskite single crystal materials possess better photoelectric properties than thin-film because of their very low defect density,long carrier transmission distance and wide absorption spectrum.In this work,CH₃NH₃PbI₃ single crystal was prepared by inverse temperature crystallization,and its physical and chemical properties were studied systematically.The results show that CH₃NH₃PbI₃ single crystal has obvious ferroelectricity.The CH₃NH₃PbI₃ single crystal self-powered photodetector based on（100）plane driven by ferroelectric polarization was realized,which shows excellent optical detection performance.CH₃NH₃PbI₃ single crystal with thickness of 50μm was prepared by space-confined inverse temperature crystallization.The effects of precursor solution concentration,solution heating rate,substrate surface tension and solvent ratio on the growth process of single crystal were investigated.It is found that CH₃NH₃PbI₃ single crystal with large grain size,high quality and controllable thickness can be obtained when the concentration of perovskite precursor solution is high,the heating rate of solution is slow,the surface tension of substrate is large and the volume ratio of solvent V_GBL:V_ACN in precursor solution is between 0.8:0.2 and 0.7:0.3.The morphology and phase structure of CH₃NH₃PbI₃ single crystal were studied by X-ray diffraction and scanning electron microscopy.It was revealed that CH₃NH₃PbI₃single crystal has flat surface and dense internal structure,which is tetragonal and（100）oriented at room temperature.The absorption spectrum of the material shows that the CH₃NH₃PbI₃single crystal material has better light absorption intensity and absorption range than the polycrystalline film.In addition,the differential scanning calorimetry curve indicated that the CH₃NH₃PbI₃ single crystal sample has a phase transition at 330 K.The in-plane amplitude hysteresis loop and phase hysteresis loop of CH₃NH₃PbI₃single crystal（100）were characterized by piezoelectric force microscope.After etching the single crystal with acetone,the domain structure of（100）crystal plane was observed by optical microscope,which shows that CH₃NH₃PbI₃ single crystal has ferroelectricity.Furthermore,the surface potential of single crystal is characterized by KPFM.It is found that there is a potential difference of-900 m V on（100）surface,and the change direction of the potential is basically the same.The self-powered photodetector driven by ferroelectric polarization on the CH₃NH₃PbI₃ single crystal（100）plane was realized for the first time.Further,the effect of temperature,channel direction and channel size on the performance of PD was systematically investigated.The self-powered photodetectors have shown excellent performance,the maximum light response is 0.16A/W,the maximum external quantum efficiency is 41.6%,the maximum on-off switching ratio is 1.41×10⁴,the maximum detection rate is 7.34×10¹¹ Jones,and the device works continuously for 2 h,the photocurrent has no attenuation,indicated the photodetector driven by spontaneous polarization could maintain long-term continuous operation.