Study On Synthesis And Photophysics Properties Of Organic Halide Perovskite Material

Since the perovskite materials CH₃NH₃ Pb Br₃ and CH₃NH₃ Pb I3 were first used by Miyasaka research group in optoelectronic devices and achieved relative higher power conversion efficiencies in 2009.Since this report,more and more attentions have been paid to the study of the synthesis and corresponding photo-physical characteristics of organic halide perovskite material CH₃NH₃ Pb X3 with different architectures.As a new promising optical material,in addition to its great potential applications in solar cells,perovskite materials also show satisfactory performance in the light-emitting field.However,some basic comprehension on photo-physical of perovskite materials,especially the dependence of crystal morphology and photo-physical properties still have not been systematically studied on.This paper is mainly aimed to resolve the above-mentioned the above problems and the main research contents of this thesis are listed as follows:?1?Set up micron-and time-resolved transient femtosecond pump-probe system with wide probe spectrum ranging from 350 to 800 nm and tunable excitation pumping ranging from 330 to 800 nm.The time resolution of the amplifier lasers is 100 fs and the test window decided by the delay line ranges 1500 ps.?2?Establish trans-missive and reflective micron-resolved absorption and fluorescence measurement system,aims to systematically study the size-dependent and local-resolved photo-physical properties of hundreds of micron-sized perovskite CH₃NH₃ Pb Br₃ cubic crystals.?3?Elucidating the band structure and photo-physical dynamics properties of free charge carrier of pure and impurities doped CH₃NH₃ Pb I3-x Clx perovskite thin films.The data demonstrated that the CH₃NH₃ Pb I3-x Clx thin film is very sensitive to the environment?the amount of annealing,humidity?,the impurity Pb I2 is very easily decomposed from perovskite crystals,which will seriously affect the photo-physical properties of the thin film;we also found that the pure perovskite crystal band structure should only have one conduction and one valence band rather than dual valences,and the pure perovskite lattice could trigger more free charge carriers with slower recombine rate under the identical pump intensity compared with the impurities doped perovskite crystal.?4?Study the role of trap-assisted recombination in luminescent properties of organometal halide CH₃NH₃ Pb Br₃ perovskite films and quantum dots by using picosecond time resolved absorption and nanosecond time resolved PL emission experiments.It was found that the integral recombination mode of CH₃NH₃ Pb Br₃ thin films was highly sensitive to the density distribution of generated charge carriers and trap states,additional,trap effects would be gradually weakened with elevated carrier densities.While the trap-assisted recombination can be removed from CH₃NH₃ Pb Br₃ QDs through its own surface passivation mechanism and this specialty may render the QDs as a new material pattern in illuminating research.?5?Studied size-dependent one-photon-?1P?and two-photon-?2P?pumped spontaneous emission?SE?and amplified spontaneous emission?ASE?from organometal halide CH₃NH₃ Pb Br₃ perovskite cubic microcrystals.The results show that the fluorescence peaks are sensitively dependent on the sizes of perovskite microcrystals,gradually red-shifting with increasing crystal sizes.Compared with 1P excitation paradigm,2P pumping is an effective paradigm to greatly reduce the thresholds by an order of magnitude due to its sharply increased gain length.Time-resolved kinetic results show that bigger-sized CH₃NH₃ Pb Br₃ perovskite cubic microcrystals shows faster life-time with higher purity.?6?Revealed the surface and bulk effect-related photo-physical properties of big-sized CH₃NH₃ Pb Br₃ cubic crystals by using micron local-and time-resolved absorption/fluorescence spectrum measurement system.In order to distinguish the bulk effect from surface effect,800 nm lasers were used to excite the perovskite crystal for its much stronger light penetration intensity compared with 400 nm lasers.The results presented in this work come to a conclusion that the band gap absorption/fluorescence of CH₃NH₃ Pb Br₃ cubic crystals are simultaneously donated to the bulk and surface transitions.