Hybrid Perovskite Single Crystal Photodetectors

As a new generation of semiconductor optoelectronic materials,organic-inorganic hybrid halide perovskites have attracted amounts of interest due to their high carrier mobility,long carrier diffusion length and larg e optical absorption coefficient.The application of new semiconductor materials in photodetectors to improve their performance has been a hot topic.Next-generation photodetectors are moving toward self-driving,high responsivity,fast response speed,low noise,broad spectral response and flexibility.Compared to polycrystalline thin films,perovskite single crystals have a lower density of trap states and no grain boundaries.They are thus expected to be able to further enhance the performance of perovsk ite photodetectors.In this thesis,organic-inorganic halide perovskite single crystals were grown and photodetectors based on these single crystals were explored.The main research contents are as follows:For the first time,a self-driven photodetector was realized by fabrication an asymmetric electrode Au-Al on the surface of the CH₃NH₃PbI₃ single crystal.The built-in electric field was effectively established by the Schottky contact between the metal and perovskite.Without bias,the response speed of the detector was 0.24 A/W.Also,it showed response within full visible spectral?375 nm?808 nm?.A planar photoconductive photodetector is prepared based on the high-quality CH₃NH₃PbI₃ single crystal grown by solution growth method assisted by chloride ion.A modified optoelectronic measurement platform was set up,in which a pulsed laser was used to replace the conventional continuous laser source,and the oscilloscope with higher sampling frequency was used as the measuring instrument.In this way,the measurement response limit of the optoelectronic platform has been greatly improved,Benif ited from the combination of the high-quality CH₃NH₃PbI₃single crystal and the greatly improved response limit of the ptoelectronic measurement platform,the real response speed of the CH₃NH₃PbI₃single crystal photodetector was measured to be less than 12.5 ns.A 2*2 photodetector array was prepared thanks to the large size and uniformity of the as-grown CH₃NH₃PbI₃ single crystal.For the first time,a speed sensor was demonstrated based on such a photodetector array.The velocity of a moving object could be calculated by the response delay between two adjacent photodetectors.In addition,capturing the trajectory of a moving object was also demonstrated.Detector noise is the key for detector sensitivity.The dark current of a photodetector determines its noise.We used methyl mixed halide perovskite CH₃NH₃Pb(Br_1-xCl_x)₃,CH₃NH₃Pb(I_1-xBr_x)₃ single crystal as the research object.The noise of a series of photodetectors based on methyl mixed halide perovskite single crystals was studied by Fast Fourier Transform.The influence of halogen doping on device noise was discussed by analyzing the noise situation.The photodector based on CH₃NH₃PbI_3-xCl_xsingle crystal with the most chlorine doping was found to have the highest noise and the lowest detection se nsitivity.The solution-grown CH₃NH₃PbI₃ single crystal was found not stable when it was stored at mother liquor at room temperature.The bulk CH ₃NH₃PbI₃single crystal tended to form hydrolyzed product which changed to CH ₃NH₃PbI₃microwires after dehydration.The CH₃NH₃PbI₃ microwires were combined with graphene and transferred to a stretchable substrate.A stretchable perovskite photodetector was successfully prepared for the first time.At 100%strain,the device still worked.With a 50%stretch,the de vice still could operate normally after 100 cycles.