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We investigated the structural properties of organic–inorganic lead halide perovskite microwires through joint experimental and theoretical Raman spectroscopy. High‐quality methyl ammonium lead iodide (MAPBI3, MA = CH3NH3+) microwires with tetragonal phases and explicit crystalline orientation were prepared. Raman spectroscopy was used in studying the as‐prepared microwires and determining not only the crystal quality but also crystalline orientation of MAPBI3 with the aid of normal mode calculations. High‐quality structural features were verified by well‐resolved Raman peaks related to the inorganic cage (IPbI stretching and bending modes below 100 cm−1), organic MA cation motions (libration ~150–200 cm−1 and torsional ~200–250 cm−1), a coupled mode of cage and MA cation liberation (~105–110 cm−1), and the almost undetectable degraded signal at 95 cm−1. In micro‐Raman mapping, an intensity ratio of 105 and 95 cm−1 was used for the direct imaging of crystal quality along the microwire. The characterization of the crystalline orientation of MAPBI3 microwires posed a challenge, which can be addressed by using polarized Raman technique with normal mode analysis. We believe that the proposed method can be extended to other organic–inorganic lead halide perovskites with different structures, such as polycrystalline films and single crystals. [ABSTRACT FROM AUTHOR]

Perovskite microwires have a larger surface-to-volume ratio and better photoelectric conversion efficiency than perovskite films. The degree of crystallization also affects the optoelectrical performances of perovskite microwires. Laser annealing was regarded as a tool for crystallization. High light absorption induced fast heating process. A 405 nm violet laser located near the absorption peak of typical perovskite films was employed as the annealing laser. In an in situ experimental design, the annealing laser beam was combined into the micro Raman measurement system. Real-time information of the annealing and crystallization was provided. Many excellent works were done, and typically needed offline optoelectronic measurements. An mW-level continuous-wave laser beam can provide enough kinetic energy for crystalline in perovskite microwires. The thermal distribution of the perovskite microwire under the annealing laser beams was considered here. Polarized Raman signals can provide evidence of the perovskite microwires crystallization. This work offered the novel approach of an on-site, real-time laser-induced thermal annealing design for perovskite microwires. This approach can be used in other material procedures. Intensity-dependent conditions were crucial for the annealing processes and analyzed in detail. The substrate effect was found. This proposed scheme provided integrated novel, scalable, and highly effective designs of perovskite-based devices. [ABSTRACT FROM AUTHOR]