Crystal structure, thermal stability and photoelectric performance of the organic-inorganic hybrid material [(CH3CH2CH2)2NH2]aBibXc (X = Cl, Br and I)

Organic-inorganic hybrid perovskites have attracted wide attention because of their low cost, high photoelectric conversion efficiency and simple production process. Diisopropylamine was innovatively employed, in this paper, as the A-site organic ligand for bismuth-based halide organic-inorganic hybrid crystals. [(CH₃CH₂CH₂)₂NH₂]_aBi_bX_c (X = Cl, Br and I) crystals were synthesized by a solvent evaporation method. All three crystals belong to the P2₁/n space group. Among them, [(CH₃CH₂CH₂)₂NH₂]BiBr₄ and [(CH₃CH₂CH₂)₂NH₂]BiI₄ have one-dimensional chain structures, and [(CH₃CH₂CH₂)₂NH₂]₂Bi₂Cl₈ belongs to a zero-dimensional structure. The band gap can be adjusted between 3.04 eV and 1.61 eV by the properties of halide ligands, and the good thermal stability of the three crystals are 203°C, 258°C and 291°C. Moreover, [(CH₃CH₂CH₂)₂NH₂]BiI₄ thin films were prepared by the one-step solution spin-coating as a light absorbing layer. The band gap of thin films is 1.97 eV. The maximum power conversion efficiency of the device is 0.0271 %. Therefore, this organic-inorganic hybrid compound with a suitable band gap and high stability is expected to become a potential candidate material for photoelectric devices.