Investigations On Growth And Optoelectronic Properties Of Large-sized CH₃NH₃PbBr₃ Perovskite Single Crystal

Organic-inorganic hybrid perovskite MAPbX₃(MA:CH₃NH₃,X:Cl,Br,I)is a serial semiconductor material with excellent optoelectronic properties,which has potential applications in photodetectors,solar cells,and high-energy detection.However,the low growth rate of single crystals results in their long-time growth periods,which hinders the CH₃NH₃PbBr₃applications in practices.In the paper,large-sized CH₃NH₃PbBr₃ single crystals were grown via the inverse temperature crystallization method and EuCl₃ assisted growth method.We deeply investigated the single crystal growth technologies,and characterized the crystal structure,optical and photoelectric properties,and finally fabricated the photodetector devices of CH₃NH₃PbBr₃ single crystals with the high performances.Our results indicated that EuCl₃ could effectively increase the growth rate of CH₃NH₃PbBr₃ single crystal and shorten the crystal growth period,without the crystalline quality decline.Moreover,the CH₃NH₃PbBr₃ single crystals grown from the EuCl₃doping precursor solution exhibit better optoelectronic performances than the one obtained from the pure solution.We attributed the performance improvements of CH₃NH₃PbBr₃ single crystals to the defect reduction due to the Eu³⁺and Cl^-.The main research results are listed as follows:(1)CH₃NH₃PbBr₃ single crystal growth using the inverse temperature crystallization method.The CH₃NH₃PbBr₃ single crystal with a size of 8mm×8mm×3mm was successfully grown using the solvent of N,N-dimethylformamide(DMF).The optical absorption edge of single crystal was at 545 nm,and then the bandgap of was estimated to be 2.27 e V.The PL emission of CH₃NH₃PbBr₃ single crystal was about 539 nm.For the CH₃NH₃PbBr₃ single crystal photodetector device,the dark current I_dark was as low as 1.25×10^-9A,and the photocurrent value I_light was 4.59×10^-5A under the laser power density of 480m W/cm² at 10V bias,and the switching ratio(I_light/I_dark)is 10⁴,the responsiveness R value is 0.08A·W^-1.(2)The wafer-level CH₃NH₃PbBr₃ single crystal was grown via inverse temperature crystallization with the EuCl₃additive.We successfully grown the CH₃NH₃PbBr₃ single crystal with a size of 28.5×25×6mm.The results showed that Eu³⁺ions assisted CH₃NH₃PbBr₃ single crystal could effectively growth at 0.38mm/h rate.A 5.0 at%at one single crystal exhibited a fast lifetime?_fast=103.86ns and a slow lifetime?_slow=739.65ns.In the performance test of the 0.5 at%EuCl₃assisted CH₃NH₃PbBr₃ single crystal photodetector,it is found that the dark current I_dark is3.85×10^-10A,the photocurrent value I_light measured under the laser power density of480m W/cm² at 10V is 1.0×10^-4A,and the switching ratio(I_light/I_dark)is 10⁵,the responsiveness R value is 0.17A·W^-1.(3)A structure composed of EuCl₃-2DMF molecule was proposed.The introduced of Eu³⁺ion as a hard Lewis acid,which has a strong interaction with DMF molecule.The phenomenon is also observed in the PL and IR spectrum.It was lead that the substituted Pb²⁺ion is finally released,and the Pb-Br_x coordination complex is formed to serve as a growth element for the CH₃NH₃PbBr₃ single crystal.EuCl₃additives can provide two functional ions,Eu³⁺and Cl^-can suppress crystal defects.On the one hand,the formation of metal Pb atom can be prevented by a reduction reaction of Eu^3+-Eu²⁺.On the other hand,few Cl^-ions can provide a halide-rich environment for the stability of Pb²⁺ions.