Phase-Pure Thiophene-Based Quasi-2D Perovskite Single Crystals via Cosolvent-Controlled Crystallization.

Area of Science:

• Materials Science
• Optoelectronics
• Crystallography

Background:

• Quasi-two-dimensional (Q2D) metal halide perovskites (PVSKs) offer enhanced stability over 3D counterparts.
• Solution-based synthesis often results in mixed phases, hindering carrier transport and device performance.
• Achieving phase-pure Q2D PVSKs is challenging due to issues like supersaturation and uncontrolled nucleation, especially with hydrophobic spacers.

Purpose of the Study:

• To develop a method for synthesizing phase-pure Q2D PVSK single crystals.
• To overcome challenges associated with hydrophobic spacers in Q2D PVSK synthesis.
• To demonstrate the improved performance of optoelectronic devices fabricated from phase-pure Q2D PVSKs.

Main Methods:

• A cosolvent-controlled crystallization method via an aqueous route was employed.
• Sulfolane was introduced as a cosolvent to control the solubility of 2-thiophenemethylammonium (TMA) and reduce precursor surface excess concentration.
• Phase purity and crystallinity were confirmed using photoluminescence (PL), X-ray diffraction (XRD), and single-crystal XRD.

Main Results:

• Phase-pure Q2D PVSK single crystals with TMA (n=1-3) were successfully synthesized.
• The method suppressed supersaturation and random nucleation, leading to highly crystalline materials.
• Photodetectors fabricated from these crystals exhibited excellent performance, including low dark current, high on/off ratio, high responsivity, high specific detectivity, and fast response times.

Conclusions:

• The cosolvent-controlled crystallization strategy effectively overcomes spacer-induced phase inhomogeneity in Q2D PVSKs.
• This work expands the library of phase-pure Q2D PVSKs.
• The synthesized phase-pure Q2D PVSKs are promising for stable, high-performance optoelectronic applications.