Composition Engineering And White Light Emission In Tin(Ⅳ) Based Metal Halide Perovskite

Metal halide perovskites（MHPs）have excellent optoelectronic properties,such as high optical absorption coefficient(>10⁵ cm^-1),large defect tolerance factor and long carrier diffusion length（>1μm）,which has attracted great research attention.The diversity of chemical composition and crystal structure provides a new platform for the development of solid luminescent materials in MHPs.In recent years,researcher has prepared a series of lead-based MHPs with high photoluminescence quantum yields（PLQY）.However,the toxicity of lead and the poor resistance to heat and humidity limit the further development of their optoelectronic applications.Therefore,nontoxic and stable perovskite alternatives must be urgently developed.Tin-based MHPs might be a good alternative for lead-based MHPs due to their similar electronic configurations.Compared to lead e,tin is non-toxic,and some tin compounds have very low toxicity and are more suitable for everyday lighting applications.In this thesis,three zero-dimensional（0D）tin-based MHPs hosts are synthesized by wet chemical method.Single or multiple metal ions are doped into the hosts resulting in white light emission.1.Bi³⁺and Te⁴⁺co-doped Cs₂Sn Cl₆ with dual emission spectrum（i.e.,450 and 575 nm）was achieved by a modified solution method,which can overcome the phase separation in the previous method for Cs₂Sn Cl₆ crystal growth.The two emission peaks arising from the two dopants Bi³⁺and Te⁴⁺have distinct photoluminescence（PL）lifetimes.Thus,the control of dopant ratio or PL delay time will regulate the PL intensity ratio between 450 and 575nm peaks leading to adjustable emission color.The energy transfer between the two emission centers,which is confirmed by the optical spectra and PL lifetime,has a criticaldistance around 7.8 nm with a maximum of 50%transfer efficiency.The Bi³⁺and Te⁴⁺co-doped Cs₂Sn Cl₆ with superior stability in water and aqua regia was fabricated into a single-phase white light-emitting diode.In the meantime,various luminescent heterostructures were obtained by epitaxial Cs₂Sn Cl₆ crystal growth with different dopants,which can broaden the study of composition engineering in halide perovskites.2.The organic cations can greatly enrich the host structures of metal halide perovskites.We have synthesized Sb³⁺@[（CH₃）₄N]₂Sn Cl₆ using a hydrothermal method,which has a broadband emission with two peaks（i.e.,490 and 653 nm）.The intensity ratio between the two emission peaks is strongly dependent on the excitation wavelength resulting in a tunable luminescence color.The two emission peaks originate from the self-trapped exciton emission from the singlet state（490 nm）and triplet state（653 nm）of Sb³⁺,respectively.The highest PLQY of Sb³⁺@[（CH₃）₄N]₂Sn Cl₆ is 59.13%when the actual doping concentration of Sb³⁺is 0.268%.In addition,Bi³⁺-doped[（CH₃）₄N]₂Sn Cl₆has blue emission（472 nm）.We can tune the white light emission by diffferent doping ratios between Bi³⁺and Sb³⁺in[（CH₃）₄N]₂Sn Cl₆.3.The major advantage of MHPs with sulfonium cations（versus ammonium cations）is the improved stability.Thus,we used the[（CH₃）₃S]⁺as the A-site in the 0D metal halide perovskite A₂Sn X₆.Sb³⁺@[（CH₃）₃S]₂Sn Cl₆ has a broadband emission with two peaks（i.e.,485 nm and 623 nm）,which intensity ratio is strongly dependent on the excitation wavelength resulting in a tunable luminescence color.White light emission with Commission Internationale de L’Eclairage of（0.38,0.31）,color rendering index of 84 and color temperature of 3825 K can be obtained under 340 nm excitation in Sb³⁺@[（CH₃）₃S]₂Sn Cl₆.When the actual doping concentration of Sb³⁺is 0.31%,PLQY can reach the highest 75%.In addition,Bi³⁺doped[（CH₃）₄S]₂Sn Cl₆has blue emission（474 nm）.We can tune the white light emission by diffferent doping ratios between Bi³⁺and Sb³⁺in[（CH₃）₄S]₂Sn Cl₆.