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 AgBi and CuBi 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. How-ever, 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 sys-tems 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)3Bi2I9 1 and (2,2-DPA)3Pb2I7 2 were con-structed. Along the path of lead-free and two-dimensional maintenance, we successfully synthesized (2,2-DPA)4AgBiI8 .H2O 3 and (2,2-DPA)4CuBiI8 .H2O 4 . As two typical semiconductors, 3 and 4 with narrower optical band gaps of 1.98 and 1.76 eV show obvious photo-response when the xenon lamp with intensity of 20 mW/cm2 is on or off, implying that they may be applied to light-harvesting and light-detecting de-vices. 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 af-ter dehydration for all we know. We believed that this work can provide meaningful guidance for the development of lead-free double perovskites.(c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.