Synthesis of Lead‐free CsGeI₃ Perovskite Colloidal Nanocrystals and Electron Beam‐induced Transformations

Abstract

Colloidal nanocrystals (NCs) of metal halide perovskite have recently aroused great research interest, due to their remarkable optical and electronic properties. We report a solution synthesis of a new member in this category, that is, all-inorganic lead-free cesium germanium iodine (CsGeI ) perovskite NCs. These CsGeI colloidal NCs are confirmed to adopt a rhombohedral structure. Moreover, the electron beam-induced transformations of these lead-free perovskite NCs have been investigated for the first time. The fracture of single-crystalline CsGeI nanocubes occurs first, followed by the emergence and growth of cesium iodine (CsI) single crystals and the final fragmentation into small debris with random orientations. Notably, the electron-reduced Ge species in CsGeI nanocubes exhibit a distinctive transformation path, compared to heavier Pb atoms in lead halide perovskite NCs.

Lead‐Free Semiconductors: Soft Chemistry, Dimensionality Control, and Manganese‐Doping of Germanium Halide Perovskites

“…In contrast to recently reported carboxylate‐capped CsGeI 3 nanocrystals, CsGeI 3 nanocrystals prepared by our method do not – unfortunately – exhibit photoluminescence (PL) emission. However, CsGeBr 3 nanocrystals exhibit a weak PL peak at 500 nm, whose intensity increases with the introduction of cysteNH 3 X, with a highest quantum yield of 0.34%.…”

“…[51] Metal doping can expand the application of semiconductor nanocrystals by introducing new or modifying existing electronic, optical and magnetic properties. [52][53][54][55] Recently, significant research focused on doping metal halide perovskites with transition or main group metals. [56][57][58] Doping with up to 46% Mn 2 + is currently possible, [59] leading to modified magnetic and optical properties.…”

Lead‐Free Metal Halide Perovskite Nanocrystals: Challenges, Applications, and Future Aspects

“…This decomposition path is a bit different from that of the heavier Pb based MHPs. The aerobic instability of CsGeX 3 perovskites due to the spontaneous oxidation of Ge 2+ to Ge 4+ is a major concern for this materials to find potential applications in optoelectronics …”

“…The analogs CsGeX 3 NCs synthesis remained unexplored, probably due to the unfavorable colloidal synthesis procedures. CsGeI 3 NCs were first synthesized by Quan et al by employing modified hot injection synthetic procedure reported by Kovalenko et al [29,58] The controlled precipitation of Cs + , Ge 2 + , I À ions into CsGeI 3 NCs were performed under an inert atmosphere using Schlenk techniques. The rapid injection of a preheated Cs-oleate precursor into Ge(II) iodide solution at 180°C in presence of OLAm, oleic acid (OLAc), and 1-octadecene (1-ODE) solvents produces highly monodispersed cubic NCs ( Figure 2).…”

Lead‐Free Halide Perovskite Nanocrystals: Crystal Structures, Synthesis, Stabilities, and Optical Properties

“…Ge‐based halide perovskites possess a formula of AGeX 3 . There has been only one report on CsGeX 3 NCs, that is, CsGeI 3 NCs that crystallize in the rhombohedral structure ( R 3 m ), as depicted in Figure e. CsGeCl 3 and CsGeBr 3 were only explored in their bulk form, which both undergo a pressure‐induced phase transition to a primitive cubic phase at room temperature. Conversely, the CsGeI 3 crystal does not encounter phase transitions during low‐temperature solution growth …”