2D Nanoplates and Scaled-Up Bulk Polycrystals of Ruddlesden–Popper Cs2PbI2Cl2 for Optoelectronic Applications

Two-dimensional (2D) layered Ruddlesden–Popper (RP) phases of halide perovskite offer exotic properties and interesting structure, which make them suitable candidates for solar photovoltaics, light emitting diodes (LEDs), and photodetector applications. Simple and scaled-up synthesis, chemical transformations, doping, and stability are the important steps toward the applications. Herein, all-inorganic RP phase of Cs2PbI2Cl2 was synthesized via a facile hot-injection method using benzoyl halides as halide sources. Different morphologies in the form of 2D nanoplates (NPLs) and small nanocrystals (NCs) were obtained by changing the concentration of capping agents (i.e., oleic acid and oleylamine) in solution. The excitonic absorption peak appeared for NPLs and NCs, which is the characteristic feature of 2D halide perovskites. Further, the scalable quantity (∼1 g) of bulk powder and micrometer-sized particles of Cs2PbI2Cl2 were synthesized via liquid assisted mechanochemical grinding and antisolvent method, respectively. We have performed post-synthetic chemical transformation to synthesize three-dimensional (3D) CsPbBr3 disk-shaped particles and zero-dimensional (0D) Cs4PbCl6 NCs from the presynthesized RP Cs2PbI2Cl2 NCs in solution and studied their optical properties. Finally, doping of Mn2+ was carried out in Cs2PbI2Cl2 NCs, which demonstrated a typical feature of Mn2+ dopant emission along with host emission properties. Low-temperature (77 K) photoluminescence (PL) spectra reveal red-shifted and line-width broadening emission along with longer PL lifetime for both undoped and Mn-doped NCs compared to room temperature PL. Further, the temperature-dependent PL spectra and thermogravimetric analysis (TGA) revealed excellent thermal stability of Cs2PbI2Cl2. This work offers an insight for exploration of the synthesis process, post-synthetic chemical transformation, and dopant insertion in all-inorganic 2D RP perovskites, which is an important step forward for application. Demonstrations of various simple syntheses of both the nanophase and bulk phase, structural transformation, and detailed optical properties of doped and undoped RP perovskite halide nanostructures unfold innovative opportunities for applicability in optoelectronics such as in solar cell and photodetectors.