In polycrystalline thin films, the inherent grain boundaries that contain abundant charge traps can cause adverse effect on optoelectronic properties of perovskite materials, and defect passivation is necessary for efficient polycrystalline PSCs. [3] In contrast, perovskite single crystals offer an opportunity to further improve the efficiency of PSCs, due to the absence of grain boundaries as well as their orders of magnitude lower defect density and longer carrier diffusion length than those in their polycrystalline counterparts. [4] Recently, the efficiency of smallarea single-crystal PSCs based on 20 µm thick MAPbI 3 (MA = CH 3 NH 3 + ) absorber layer has reached 21.9% by using a low-temperature (<90 °C) inverse temperature crystallization (ITC) method. [5] Moreover, the near-infrared response of the devices can be expanded by incorporating FA (FA = CH(NH 2 ) 2 + ) into MAPbI 3 crystals, leading to a high PCE of up to 22.8%. [6] To construct large-area single-crystal PSCs, Liu et al. developed a refreshing-reiteration method to grow perovskite bulk single crystals with dimension as large as 120 mm. [7] Besides, they established a diamond-wire-sawing process to produce inchsized single-crystal perovskite wafers for fabrication of inchsized single-crystal PSCs. [8] For photovoltaic application, growth of micrometer-thick lead-iodide perovskite single crystals is necessary to promote carrier transport and collection. [9] Liu et al. designed an ultrathin geometry-defined dynamic-flow reaction system and realized the growth of large-area single-crystal perovskite wafers with controllable thickness, which provides a universal and effective strategy for application of perovskite single crystals in optoelectronic device design and fabrication. [10] In this method, a mass concentration of defects would unavoidably be generated at the interface due to the lattice mismatch between perovskite and hole transport layer (HTL). Huang et al. found that the trap density in perovskite single crystals increased by five orders of magnitude from interior to surface/interface, and most deep traps were detected near the HTL/perovskites interface. [11] On the other hand, the ion diffusion rate in the confined space is limited by the interaction between substrates and solvated Perovskite single crystals have recently been regarded as emerging candidates for photovoltaic application due to their improved optoelectronic properties and stability compared to their polycrystalline counterparts. However, high interface and bulk trap density in micrometer-thick thin single crystals strengthen unfavorable nonradiative recombination, leading to large open-circuit voltage (V OC ) and energy loss. Herein, hydrophobic poly(3-hexylthiophene) (P3HT) molecule is incorporated into a hole transport layer to interact with undercoordinated Pb 2+ and promote ion diffusion in a confined space, resulting in higher-quality thin single crystals with reduced interface and bulk defect density, suppressed nonradiative recombination, accelerated charge transp...

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.

Organic single crystals play indispensable roles in high-performance electronic devices because of their completely eliminated or minimized impurities and disorder, wherein ultrathin thickness is a critical prerequisite because charge accumulation in devices occurs within a few molecular monolayers of the semiconductors. The growth of organic crystals through vapor dispels concerns about solubilities and the inclusion of solvents in the final crystals, but achieving an ultrathin thickness for common organic semiconductors is beyond its power. On the basis of our recently invented microspacing in-air sublimation (MAS), the distance between the source and growth position is set to approximate the mean free path of the vaporized molecules. Such a configuration generates a genetic relationship between the morphology of the source materials and that of the grown crystals. By refining the deposition of the source materials using ultrasonic spray, we can obtain ultrathin single crystals with a uniform distribution. We exemplify the strategy through MAS growth of ultrathin DNTT and pentacene single crystals down to five and three molecular monolayers, respectively. Field effect transistors fabricated on the ultrathin crystals exhibited average charge carrier mobilities of 6.08 cm 2 V −1 s −1 for DNTT and 2.39 cm 2 V −1 s −1 for pentacene, and low threshold voltages (∼83% of the devices within 5 V).

Although the room-temperature phosphorescence (RTP) organic material is a long-studied topic and has become especially popular in the recent decade, all-round players with qualified long-lived RTP lifetimes to fulfill the...

Perovskite single crystals and polycrystalline films have complementary merits and deficiencies in X‐ray detection and imaging. Herein, we report preparation of dense and smooth perovskite microcrystalline films with both merits of single crystals and polycrystalline films through polycrystal‐induced growth and hot‐pressing treatment (HPT). Utilizing polycrystalline films as seeds, multi‐inch‐sized microcrystalline films can be in situ grown on diverse substrates with maximum grain size reaching 100 μm, which endows the microcrystalline films with comparable carrier mobility‐lifetime (μτ) product as single crystals. As a result, self‐powered X‐ray detectors with impressive sensitivity of 6.1×104 μC Gyair−1 cm−2 and low detection limit of 1.5 nGyair s−1 are achieved, leading to high‐contrast X‐ray imaging at an ultra‐low dose rate of 67 nGyair s−1. Combining with the fast response speed (186 μs), this work may contribute to the development of perovskite‐based low‐dose X‐ray imaging.