Abstract
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.
Highlights
Since Ashkin et al developed optical trapping with the use of a tightly focused laser beam in 1986, this technique has been widely used as an optical tweezer for trapping and manipulating small dielectric micro- and nanoobjects[1,2]
The crystal formed in the MAPbBr3 precursor solution showed green emission resulting from two-photon absorption of the trapping laser (λ = 1064 nm), whereas two-photon excited emission was not detected from the mixed chloride–bromide perovskite crystals
To further understand the influence of laser heating on crystal nucleation and growth under optical trapping, we investigated spontaneous crystallization during heating in the unsaturated precursor solution of MAPbBr2.5Cl0.5, but without any laser irradiation
Summary
Since Ashkin et al developed optical trapping with the use of a tightly focused laser beam in 1986, this technique has been widely used as an optical tweezer for trapping and manipulating small dielectric micro- and nanoobjects[1,2]. Laser trapping has played an innovative role in biological research by the noninvasive manipulation of microorganisms and organelles[3,4,5]. In chemistry, this technique was applied to smaller objects, such as nanoparticles[6], quantum dots[7], polymers[8], proteins[9], and amino acids[10], confining and assembling those in the focal volume.
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