Organic cocrystals possess valuable properties owing to the synergistic effect of the individual components. However, the growth of molecular cocrystals is still in its primary stage. Here we develop a microspacing in-air sublimation method to grow organic cocrystals, and furthermore to realize morphology control on them, which is essential for structure–property relations. A series of polycyclic aromatic hydrocarbon (PAH)‒1,2,4,5-tetracyanobenzene (TCNB) complexes cocrystals are grown directly on the substrate, with the morphology tunable from 1D needle-like to 2D plate-like on demand. Spatially resolved photoluminescence spectra analyses on different cocrystals display morphology dependent and anisotropic optical waveguiding properties. In situ observation and energy calculations of the crystallization processes reveal the formation mechanism being from a competition between growth kinetics-defined crystal habit and the thermodynamics driving force. This growth technique may serve the future demand for tunable morphology organic cocrystals in different functional applications.

Organic single crystals manifest the intrinsic physical properties of materials. However, traditional growth of organic single crystals is limited by low solubility from solutions or complexity from physical vapor deposition. Here we report a new method to grow organic single crystals by microspacing in-air sublimation, which avoids costly vacuum system and time-consuming procedures and is practical for a wide range of organic crystals. In situ crystal growth observation revealed an unprecedented vapor-to-melt-to-crystal mechanism, resulting from the micrometer scale spacing distance between the source and the growth position. FET devices based on the rubrene crystals directly grown on Si/SiO2 substrate exhibited higher mobility than the best record using SiO2 as the gate dielectric. This effective organic crystal growth technique can be affordable and handled for almost every lab, which may be beneficial for future research and application of organic crystals.

The emergence of organic–inorganic halide perovskites has reformed the research status of optoelectronics to a great extent. The bulk single crystals of halide perovskite, which in theory reflect the intrinsic physical properties of the material, are however hard to integrate into functional devices. Just as in the case that silicon wafers have revolutionized modern industries including electronics and solar cells, the availability of perovskite crystal wafers may pave the way to functional devices. Here we designed a new settled temperature and controlled antisolvent diffusion system to precisely control all key factors that affect the supersaturation metastable zone during the crystal growth process, to grow MAPbBr3 single crystals more than 50 mm in size. Second, we fabricated MAPbBr3 single crystal wafers with different orientations, specifically, the (100), (010), (001), (110), and (111) wafers, with high crystalline quality (half-peak width of rocking curve of 60–100 arc sec). Some key parameters were measured and compared on the wafers, where the results hint that anisotropy of carrier transport may exist for this pseudocubic structure. We hope the availability of oriented single-crystal wafers can provide more scientists the materials and devices to clarify the debatable physicochemical properties and to integrate the wafers as active layers or substrates in optoelectronic devices.

Mixed halide coordination has been widely used to finely tune the properties of inorganic and inorganic− organic hybrid compounds, especially for emerging perovskites materials. Despite the increasing number of reports on preparation methods and the affected functionalities, the peculiar and precise role of the doping halogens in structural regulation of the crystals and the resulting variations on the basic properties remain to be addressed. Here, to shed light into the "black box", a new series of [NH 2 (CH 2 CH 3 ) 2 ] 3 Bi(Cl 1−x Br x ) 6 (x = 0, 0.135, 0.255, 0.385, 0.847, and 1) single crystals were grown from the mixed halide solvents by the temperature lowering method. The correlation between the inclusion amounts of Br in the final crystals with the halide concentrations in the precursors is discussed from different perspectives. The two kinds of halogens share the same position in the mixed halide system, with every crystallographically independent halide site possessing different halogen occupancies. The mixed halide coordination exhibits a regulated effect on the distortion of the anion octahedra. Optical absorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and the second harmonic generation (SHG) measurements have confirmed that, with increased Br inclusion, [NH 2 (CH 2 CH 3 ) 2 ] 3 Bi(Cl 1−x Br x ) 6 crystals exhibit a regulated effect on their bandgaps, thermal stabilities, and SHG capacities.

It has been proved that bulk single crystals of a halide perovskite behave much better than its polycrystalline counterparts in multiple application scenarios. Thus, the growth of large-sized and high-quality single crystals is significant to guarantee their ultimate device performances. Here, based on our recently invented settled temperature and controlled antisolvent diffusion system, improvements achieved in this work include the following: (1) We modified the growth system to optimize the control over both mass and heat transport to alleviate defect formation. State-of-the-art-quality MAPbBr3 crystals were grown, and from the bulk crystals, differently oriented crystalline wafers were fabricated with the full width at half-maximum of X-ray rocking curves of 40–86 arcsec. (2) The optical band gaps revealed no anisotropy on differently oriented wafers, whereas the refractive index and extinction coefficient exhibited obvious anisotropy. (3) Angle-resolved polarized Raman spectra demonstrate distinct in-plane anisotropy on (100) and (110) wafers but not on the (111) wafer. The equilibrium MA+ orientations are deduced to adopt the <111> direction with the antiparallel MA+ orientation between adjacent domains. (4) Radiation detectors fabricated on differently oriented wafers proved photoresponse anisotropy to both visible and X-ray radiation, following a general order of (100) > (110) > (111). Because anisotropy is an inevitable issue for various applications employing crystalline materials, this study, based on the clarification of the debatable intrinsic dipole configuration in the pseudocubic crystal lattice, will provide quantitative information on physicochemical property anisotropy and subsequently facilitate optimization of device performance referring to crystal orientations of halide perovskite crystals.