Low-dimensional metal halides at molecular level, which feature strong quantum confinement effects from intrinsic structure, are emerging as ideal candidates in optoelectronic fields. However, developing stable and nontoxic metal halides still remains a great challenge. Herein, for the first time, high-crystalline and highly stable CsCu 2 I 3 single crystal, which is acquired by a low-cost antisolvent vapor assisted method, is successfully developed to construct high-speed (t rise /t decay = 0.19 ms/14.7 ms) and UV-tovisible broadband (300-700 nm) photodetector, outperforming most reported photodetectors based on individual all-inorganic lead-free metal halides. Intriguingly, facet-dependent photoresponse is observed for CsCu 2 I 3 single crystal, whose morphology consists of {010}, {110}, and {021} crystal planes. The on-off ratio of {010} crystal plane is higher than that of {110} crystal plane, mainly owing to lower dark current. Furthermore, photogenerated electrons are localized in twofold chains created by [CuI 4 ] tetrahedra, leading to relatively small effective mass and fast transport mobility along the 1D transport pathway. Anisotropic carrier transport characteristic is related to stronger confinement and higher electron density for {110} crystal planes. This work not only demonstrates the great potential of CsCu 2 I 3 single crystal in high-performance optoelectronics, but also gives insights into 1D electronic structure associated with fast photoresponse and high anisotropy.

moderate UV light is beneficial for human health, however, excessive UV radiation can cause various human diseases as well as strong destruction to the output of crops and the lifespan of buildings. [1b,3a,4] Therefore, an efficient detection of UV radiation is of significant importance in widespread applications, for example, chemical, environmental, and biological analysis or warning, astronomical investigation, and optical communication. [1c,5] For forewarning UV radiation with high-efficiency, a wide variety of UV PDs such as photomultiplier and silicon diode, have been extensively investigated and applied in the past decades. Nevertheless, there are intrinsic imperfections for the present commercial PDs, such as fragile, large volume, and excessive cost, which are obstacles when meeting the growing requirement of miniaturized and reliable UV detection devices for portable or shipped applications. In recent years, the development of semiconductor-based PDs that work according to the photoelectric effect has received great research interest. [1b,3a,6] In this scenario, a delicate selection of suitable materials with efficient morphological, microstructural, and photoelectrical characteristics plays a key role in the construction of PDs with high-performance. Generally, the PDs work following several different physical mechanisms, that is, surface plasma-wave-assisted effect, photoconductive effect, photothermoelectric effect, and photovoltaic effect, which have been systematically demonstrated in the previous report. [7] More recently, a new generation of wide-bandgap semiconductors including the classification of nitrides (GaN, AlN, BN, etc.), carbides (SiC, diamond, etc.), sulfides (ZnS, etc.), oxides (ZnO, Ga 2 O 3 , TiO 2 , etc.), halide perovskites (e.g., CH 3 NH 3 PbCl 3 ), [8] and their combinations, is emerged as the most attractive material candidates for constructing high-performance UV PDs, owing to their unique advantages, for instance low permittivity, high breakdown electric-fields, good thermal conductivity, high electron saturation rates, excellent radiation resistance, and their appropriate spectral range for UV response. [1d] In addition, the photoelectric conversion processes of the semiconductorbased PDs can be generally described by the behaviors of charge carriers, such as their generation, separation, transportation, and extraction. [9] Therefore, any factor that influences the photon-generated carrier behaviors should be the key parameter for further tuning their photodetecting performances. It As a wide-bandgap semiconductor material, titanium dioxide (TiO 2 ), which possesses three crystal polymorphs (i.e., rutile, anatase, and brookite), has gained tremendous attention as a cutting-edge material for application in the environment and energy fields. Based on the strong attractiveness from its advantages such as high stability, excellent photoelectric properties, and lowcost fabrication, the construction of high-performance photodetectors (PDs) based on TiO 2 nanostructures is ...

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higher carrier mobility and longer carrier lifetime, thanks to their fewer grain boundaries, enhanced crystallinity and reduced trap density. With such performance improvements, the lead-free halide perovskite single crystal is considered to be a promising photosensitive material in optoelectronic devices. [6] In order to effectively promote power conversion efficiency, the thickness of leadfree halide perovskite single crystal should be controlled at a suitable level, which is suggested to be greater than light-absorption length and less than carrier-diffusion length. [7] In the current semiconductor and photoelectronic industries, thin silicon wafers are fabricated mainly through top-down process, which requires high yields accompanied with large material loss, waste and subsequent complicated slicing process. Against this background, a facile and effective space-confined fabrication is adopted to produce large singlecrystalline thin film, through a bottom-up process. [8] Compared with vapor epitaxial growth and cavitation triggered asymmetrical crystallization, [9] space-confined methods possess moderate growth conditions to grow SCTF without rigorous restrictions. However, this method is limited to the growth of organic-inorganic lead halide perovskite SCTF, few studies focus on lead-free halide perovskite SCTF, such as Sn-based, Bi-based and Sb-based, etc. This is limited by the lack of understanding of the precursor solution chemistry in space-confined method. [10] Although previous work pointed out that the preheated-substrate and local heating are important in the space-confined growth, [11] there is a lack of investigation on the influence of the precursor solution temperature on the crystallization process. In general, the growth drive force of the space-confined growth is considered to be inverse-temperature crystallization or solvent evaporation, in which the supersaturation plays a key role in controlling size and quality. [12] An indepth insight of the relationship between the nucleation and crystallization process in the precursor solution is of significant importance. Therefore, it is necessary to clarify the effects of supersaturation in the space-confined growth.Furthermore, the space-confined method demonstrates the advantage of substrate-independent characteristics, which facilitate convenient integration of lead-free halide perovskite SCTF Monolithical integration of the promising optoelectronic material with mature and inexpensive silicon circuitry contributes to simplifying device geometry, enhancing performance, and expanding new functionalities. Herein, a leadfree halide perovskite Cs 3 Bi 2 I 9 single-crystalline thin film (SCTF), with thickness ranging from 900 nm to 4.1 µm and aspect ratio up to 1666, is directly integrated on various substrates including Si wafer, through a facile and lowtemperature solution-processing method. The growth kinetics of the lead-free halide perovskite SCTF are elucidated by in situ observation, and the solution supersaturation is controlled to reduce the ...

An organic photodetector (OPD), with organic semiconductors as photosensitive layer, has proved to rival that of a low-noise silicon photodetector, almost in all metrics [10] and has promising applications in health monitoring and image sensing. [11][12][13] In the meantime, flexible organic semiconductors are advantageous substitutes for inorganic semiconductors in wearable electronics because conformal thin-film devices can be manufactured with them, therefore, can better adhere and fit human skin. [14,15] Although organic semiconductors can make up for the poor flexibility of inorganic semiconductors to some extent, the metal-based or metal oxide electrodes in OPD remain a block to the realization of ultraflexible devices. [13] Simultaneously, metal-based or metal-oxide-based electrodes require vacuum thermal evaporation or electron beam deposition techniques that will complex the preparation process and increase production costs. [15] Introducing intrinsic flexible organic electrodes may help solve the above mentioned problems. The polymer conductor poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PH1000 (PH1000) with superb transmittance and conductivity, which can be fabricated by a simple solution method, has proved to be the most promising electrode in skin-like wearable electronics. [1] Dual-polarity photocurrent response endows optoelectronic devices with multifunctional characteristics that have proved to be applied in switchable light imaging, optical communication, and spectral bands' distinction. [16][17][18][19] While traditional p-n junction photo diodes should obey the physical principles of the unidirectional current migration, hence dual-polarity photocurrent response in the previous researches was realized by taking advantage of the concomitance among photovoltaic, photo-electrochemical, and photo-thermoelectric effects, [16,17,20,21] which has a high demand in selecting materials and fabricating devices. While in organic semiconductor systems, donors and acceptors blended to form interpenetrating bulk-heterojunction (BHJ) networks, [22] by reasonably designing the work functions of electrodes, migrations of electrons/holes can be effectively regulated thus can easily switch the polarity of electronic signals. [23,24] Distinctive characteristics of BHJ in OPD inspired us a straightforward and low-cost way in developing dual-polarity photocurrent response optoelectronic devices.In this work, we introduced transparent organic electrodes PH1000/PH1000 to fabricate an all-organic photodetector (all-OPD) with a vertically aligned structure PH1000/ poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), Al 4083Endowing photodetectors with mechanically flexibility and actual functionality are current research issues in developing optoelectronic devices. However, rigid metal-based or metal-oxide-based electrodes remain a block to the realization of ultraflexible electronics. Thus, an ultraflexible all-organic photodetector (all-OPD) is designed by innovatively introducing symmetrical organic ...

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Tunable work function has a high profile for the MXene-based optoelectronic devices, and surface modification provides the huge potential to shift its Fermi level and modulate the work function. In this work, the window of MXene's work function is engineered from 4.55 to 5.25 eV by surface modification with LiF, Se, and polyethylenimine ethoxylated (PEIE). The vertical p-CsCu 2 I 3 /n-Ca 2 Nb 3-x Ta x O 10 junction photodetectors are constructed on the basis of the above surfacemodified MXenes, which changes the Schottky barrier between n-Ca 2 Nb 3-x Ta x O 10 and the electrodes. In particular, the rectification effect is significantly enhanced by utilizing PEIE-decorated MXene electrodes, resulting in a high rectification ratio of 16 136 and improved UV responsivity of 81.3 A W -1 . Such high-performance devices based on MXenes electrodes are compatible with the standard clean room fabrication process, realizing large-scale flexible UV detectors that maintain 80% of the original current after 5000 times bending. Meanwhile, a photodetector array stimulated with UV of different wavelengths is constructed to reveal its potential for image sensing. Finally, functional "AND" and "OR" optoelectronic logic gates are developed for UV communication using Au/ CsCu 2 I 3 /Ca 2 Nb 3-x Ta x O 10 /MXene-PEIE photodetectors, enriching the application of MXene-based optoelectronic devices. This work on tuning MXene work function via surface modification demonstrates that MXene is a promising candidate for future optoelectronics.

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