Mixed-halide perovskite synthesis by chemical reaction and crystal nucleation under an optical potential

• Published in: NPG Asia materials Vol. 11; no. 1; pp. 1 - 7
• Main Authors: Islam, Md Jahidul, Yuyama, Ken-ichi, Takahashi, Kiyonori, Nakamura, Takayoshi, Konishi, Katsuaki, Biju, Vasudevanpillai
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 28.06.2019; Nature Publishing Group
• Subjects: 639/301/1005/1007; 639/638/298/398; Biomaterials; Chemical reactions; Chemical synthesis; Chemistry and Materials Science; Chloride; Chlorides; Composition; Crystal growth; Crystals; Energy Systems; Fluorescence; Free energy; Lead compounds; Materials Science; Metal halides; Nucleation; Optical and Electronic Materials; Optical materials; Optical properties; Optics; Optoelectronics; Organic chemistry; Perovskites; Photoluminescence; Photovoltaic cells; Precursors; Single crystals; Solar cells; Structural Materials; Surface and Interface Science; Thin Films; X-ray diffraction
• ISSN: 1884-4049; 1884-4057
• DOI: 10.1038/s41427-019-0131-0

The development of new methods to engineer lead halide perovskite crystals with a controlled band gap and emission properties is an active subject in materials science and chemistry. We present the preparation of mixed-halide lead perovskites by spatially- and temporally- controlled chemical reactions and crystal growth under an optical potential in unsaturated precursor solutions. The crystals are characterized by transmission and photoluminescence spectral measurements and X-ray diffraction analysis. When compared with the spontaneous formation of multiple crystals in saturated precursor solutions, the optical potential creates large single crystals with a high chloride composition, providing distinct blue and green fluorescent crystals of chloride–bromide lead perovskites. We discuss the formation of mixed-halide perovskites from the viewpoints of an increased rate of chemical reaction via the formation and desolvation of precursor complexes and a decreased free energy potential. Optical materials: laser trapping for halogen mixed perovskite single-crystal synthesis A technique that uses lasers to control chemical reactions has been shown by researchers in Japan to modify the optical properties of photovoltaic materials. Lead halide perovskites have emerged recently as an exciting option for optoelectronic applications, particularly solar cells. This technology requires a method that can produce large-area samples with high crystalline quality. Ken-ichi Yuyama, Vasudevanpillai Biju, and their colleagues from Hokkaido University, focused laser light in a precursor solution, which increased the concentration of molecules and initiated chemical reaction and crystal growth. This precise chemical control enabled the synthesis of highly luminescent chloride–bromide lead perovskite single crystals with a higher chloride composition than is possible using spontaneous crystal formation. The extra chloride shifted the optical fluorescence of the material into the blue part of the spectrum. Laser trapping chemistry is applied to synthesize single crystals of pure and mixed halide lead perovskites in a temporally- and spatially- controlled manner. Thus, we obtain perovskite crystals with controlled band gap or photoluminescence color. The formation mechanism of a perovskite crystal is discussed in terms of an increased rate of chemical reaction of precursors collected by the trapping leaser.