Publication date: 22nd July 2026
Single-crystal halide perovskites provide a powerful platform for probing intrinsic structure–property relationships and for translating controlled crystal growth into high-performance optoelectronic and emerging devices. In this invited talk, I will use our work on in situ organic cation chemistry to illustrate how precursor reactivity can be used to grow and engineer hybrid halide perovskite single crystals. In this approach, amide solvents such as N-methylformamide and N-dimethylformamide act not only as solvents, but also as sources of organic ammonium cations generated under acidic conditions. This chemistry first enabled the room-temperature growth of bulk methylammonium lead halide crystals without relying on pre-synthesized organic ammonium halide salts [1].
The talk will focus on how this approach links precursor chemistry to crystal growth, compositional control, defect formation, lattice strain, surface quality, and device response. I will discuss mixed dimethylammonium/methylammonium lead bromide crystals as a case study in A-site organic-cation engineering, where cation mixing suppresses structural phase transitions, modifies organic-cation dynamics, and enhances photodetection [2]. Related studies further reveal that precursor composition and concentration can promote the formation of metallic lead during crystallization, highlighting the need to understand solution chemistry as an active contributor to defect formation in halide perovskite single crystals [3].
Building on this link between crystallization chemistry and optoelectronic response, I will also discuss methylammonium lead bromide single crystals with compressed emissive edges, produced by manipulating in situ cation generation and the crystallization process. This example shows how spatially non-uniform crystallization can create persistent local lattice compression within a single crystal, leading to edge-selective emission and improved photodetector response [4]. Finally, I will discuss surface-engineered MAPbBr3 crystals in which an in situ-grown polycrystalline passivating layer reduces surface defects, improves X-ray detection, and enhances photodetector performance [5,6].
As a brief outlook, I will also show how related in situ organic cation chemistry can be extended to lead-free layered copper halides, where local structure, halide vacancies, and ion migration govern resistive switching behavior [7]. Together, these studies show that in situ organic cation chemistry offers more than an alternative synthetic route. It provides a chemical framework for designing halide perovskite single crystals and related crystalline materials with controlled defects, engineered surfaces, and device-relevant functionality.
The work summarized in this talk was carried out with the contributions of many students, postdoctoral researchers, collaborators, and co-authors, whose efforts are gratefully acknowledged.
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