Construction, photoelectric response and phase transition for new hybrid double perovskites showing narrow band gaps

To explore the lead-free key scientific issue in perovskite, double perovskite based on Ag Bi and Cu Bi was naturally selected as a competitive candidate due to its fascinating functional features, such as self-powered circularly polarized light detection, X-ray detection, photoluminescence and so on. However, the most challenging point is to simulate the structure and function of traditional lead-based perovskite in new double perovskite. At the same time, there are few suitable double perovskite systems with optical and electrical potential. The above two points greatly limit the competitiveness of double perovskite. In order to solve this problem, firstly, by analyzing and comparing previous studies,we used 2,2-dimethylpropan-1-aminium(abbreviated as 2,2-DPA) as the organic template to assemble materials. Solid-to-solid phase transition materials(2,2-DPA)3Bi2I91 and(2,2-DPA)3Pb2I72 were constructed. Along the path of lead-free and two-dimensional maintenance, we successfully synthesized(2,2-DPA)4AgBiI8.H_(2)O 3 and(2,2-DPA)_(4)CuBiI8.H_(2)O 4. As two typical semiconductors, 3 and 4 with narrower optical band gaps of 1.98 and 1.76 e V show obvious photo-response when the xenon lamp with intensity of 20 m W/cm^(2)is on or off, implying that they may be applied to light-harvesting and light-detecting devices. By referring to the phase transition mechanism of 1 and 2, 3 may be caused by ordered-disordered transition of the organic part, which was proven to be the first solid-to-solid phase transition material with <100>-oriented layered double perovskites with n = 1 by systematic characterization methods after dehydration for all we know. We believed that this work can provide meaningful guidance for the development of lead-free double perovskites.

X-site doping in ABX_(3) triggers phase transition and higher T_(c) of the dielectric switch in perovskite

Material stability is always the key factor for applied materials especially the working environment that requires higher temperature sensitivity or temperature fluctuation range.In which,the stimulus-response perovskite materials are just sensitive to stability to ensure the accuracy and stability of the signals,in the applied devices of batteries and memory storage devices and so on.However,it is still a tremendous challenge to improve the stability of perovskite materials,and maintain reliability in the devices.Here,a novel ABX_(2)X'_(1)(X-site doping in an ABX_(3))compound[CEMP]-[CdBr_(2)(SCN)](1,CEMP=1-(2-chloro-ethyl)-1-methyl-piperidine)with remarkable high-temperature reversible dielectric switching behavior was proposed.The strategy of[SCN]^(−)doping in perovskite for improving the stability was successfully achieved.Meanwhile,the steric hindrance is increased while the energy barrier is also increased by replacing hydrogen with flexible groups,which leads to a high-temperature reversible phase transition.The new finding provides a new direction to enrich new applications and design ideas of perovskite materials.Especially the X-site strategy of doping or substitution in the ABX_(3),it will promote ingenious and perfect experimental results in material synthesis and performance improvement by chemistry disciplines.

Hybrid Optical-Electrical Perovskite Can Be a Ferroelastic Semiconductor

Organic–inorganic hybrid perovskites(OIHPs)have been a hot research topic due to their advanced structural and functional features that cover almost all the research fields of intelligent materials including ferroelectric,photovoltaic,fluorescent,and dielectric.However,the development of the construction of an OIHP ferroelastic semiconductor with optical-electrical response has been a huge challenge and infrequently reported.In this work,a rare and interesting hybrid perovskite ferroelastic semiconductor,[BFDA]PbBr_(3)(BFDA=benzyl-(2-fluoro-ethyl)-dimethyl-ammonium),was synthesized,which benefits from the structural advantage of a long tail BFDA to be balanced by the suitable inorganic framework.[BFDA]PbBr_(3) shows a high-temperature ferroelastic phase transition at 365 K and a direct band gap of 3.33 eV.In addition,it can emit charming orange-pink light under a 365 nm UV lamp.To combine this with the ferroelastic,optical,and dielectric properties,[BFDA]PbBr_(3) can be identified as a very rarely reported ferroelastic semiconductor.The above-mentioned synthesis strategy is also helpful for the enrichment and development of the hybrid perovskite family.