Centimeter-scale 2D perovskite (PEA)2PbBr4 single crystal plates grown by a seeded solution method for photodetectors.

Large-sized single-crystal two-dimensional (2D) perovskites are highly desirable owing to their fundamental properties and intriguing ability to boost devices. Herein, 2-phenylethylammonium lead bromide [(PEA)2PbBr4] single crystals, which are a violet-light-emitting 2D perovskite material, with typical lateral sizes of about one centimeter were successfully grown using a seeded solution method. The single-crystal plates showed a well-defined shape (rectangle or hexagon), a natural thickness (300-500 µm) similar to that of conventional silicon and InP wafers, a large aspect ratio of ∼20, and a smooth surface (root mean square, ∼0.7 nm). We integrated these single crystal plates into an ultraviolet photodetector, achieving a low dark current of ∼10-13 A and an efficient photoresponse (on/off ratio, ∼103). This experiment could easily be extended to grow freestanding 2D perovskite single crystals on a wafer scale for practical integrated optoelectronics.

Low-threshold room-temperature continuous-wave optical lasing of single-crystalline perovskite in a distributed reflector microcavity.

Organic-inorganic halide perovskites have achieved remarkable success in various optoelectronic devices. A high-quality CH3NH3PbBr3 single-crystalline thin film has been directly grown in a micrometer gap between a pair of distributed reflectors with over 99.9% reflectivity, which naturally form a vertical cavity surface-emitting laser device with a single mode or several modes. The single-crystalline perovskite has an exciton lifetime of 426 ns and evidence of the exciton-photon coupling is observed. At room temperature and under continuous-wave optical pumping conditions, this device lases at a threshold of 34 mW cm-2 in the green gap. The extremely low lasing threshold suggests that polariton lasing may occur in the strongly confined optical cavity comprising the high-quality single-crystalline perovskite.

Acetone vapour-assisted growth of 2D single-crystalline organic lead halide perovskite microplates and their temperature-enhanced photoluminescence.

We adopt an acetone vapour-assisted method to grow high quality single-crystalline microplates of two-dimensional (2D) perovskite, 2-phenylethylammonium lead bromide [(C6H5C2H4NH3)2PbBr4]. The microplates, converted from the spin-coated films, are well-defined rectangles. Temperature dependent photoluminescence (PL) spectroscopy shows that the band gap PL is enhanced markedly with increasing temperature up to 218 K, accompanied by the quenching of the PL related to the trap states, which perhaps results from the exciton-phonon couplings. The optical phonon energy around 50 meV and the exciton binding energy around 120 meV are derived by fitting the band gap PL linewidths and intensities at different temperatures, respectively.