Quantum spin liquid (QSL) is a novel state of matter which refuses the conventional spin freezing even at 0 K. Experimentally searching for the structurally perfect candidates is a big challenge in condensed matter physics. Here we report the successful synthesis of a new spin-1/2 triangular antiferromagnet YbMgGaO4 with symmetry. The compound with an ideal two-dimensional and spatial isotropic magnetic triangular-lattice has no site-mixing magnetic defects and no antisymmetric Dzyaloshinsky-Moriya (DM) interactions. No spin freezing down to 60 mK (despite θw ~ −4 K), the power-law temperature dependence of heat capacity and nonzero susceptibility at low temperatures suggest that YbMgGaO4 is a promising gapless (≤|θw|/100) QSL candidate. The residual spin entropy, which is accurately determined with a non-magnetic reference LuMgGaO4, approaches zero (<0.6%). This indicates that the possible QSL ground state (GS) of the frustrated spin system has been experimentally achieved at the lowest measurement temperatures.

All-inorganic perovskites have high carrier mobility, long carrier diffusion length, excellent visible light absorption, and well overlapping with localized surface plasmon resonance (LSPR) of noble metal nanocrystals (NCs). The high-performance photodetectors can be constructed by means of the intrinsic outstanding photoelectric properties, especially plasma coupling. Here, for the first time, inorganic perovskite photodetectors are demonstrated with synergetic effect of preferred-orientation film and plasmonic with both high performance and solution process virtues, evidenced by 238% plasmonic enhancement factor and 10 on/off ratio. The CsPbBr and Au NC inks are assembled into high-quality films by centrifugal-casting and spin-coating, respectively, which lead to the low cost and solution-processed photodetectors. The remarkable near-field enhancement effect induced by the coupling between Au LSPR and CsPbBr photogenerated carriers is revealed by finite-difference time-domain simulations. The photodetector exhibits a light on/off ratio of more than 10 under 532 nm laser illumination of 4.65 mW cm . The photocurrent increases from 0.67 to 2.77 μA with centrifugal-casting. Moreover, the photocurrent rises from 245.6 to 831.1 μA with Au NCs plasma enhancement, leading to an enhancement factor of 238%, which is the most optimal report among the LSPR-enhanced photodetectors, to the best of our knowledge. The results of this study suggest that all-inorganic perovskites are promising semiconductors for high-performance solution-processed photodetectors, which can be further enhanced by Au plasmonic effect, and hence have huge potentials in optical communication, safety monitoring, and biological sensing.

Image sensor arrays are widely used in digital cameras, smartphones, and biorobots. However, most commercial image arrays rely on the dichroic prisms or a set of interference filters to distinguish characteristic color spectrum, which significantly increases the cost and fabrication processing complexity. In this work, an ultranarrow response photodetector with full-width at half-maximum being ∼12 nm and specific detectivity over 1011 Jones at 545 nm are successfully achieved in CsPbBr3 polycrystalline films using freeze-drying casting method to adjust the surface-charge recombination. To our best knowledge, this is the narrowest spectrum response for perovskite photodetectors in the visible light waveband. More importantly, a series of narrowband photodetectors are developed to enhance diverse selectivity for target signals covering from blue light to red light via bandgap tuning in CsPbX3 by tailoring the halide component. Finally, an integrated sensing array with CsPbX3 (X = Cl, Br, I) narrowband photodetectors acting as color recognition cones is constructed, which presents clear color and shape recognition paving the way for commercialization of perovskite photodetector in artificial vision.

Transition metal dichalcogenides (TMDs) are promising candidates for flexible optoelectronic devices because of their special structures and excellent properties, but the low optical absorption of the ultrathin layers greatly limits the generation of photocarriers and restricts the performance. Here, we integrate all-inorganic perovskite CsPbBr nanosheets with MoS atomic layers and take the advantage of the large absorption coefficient and high quantum efficiency of the perovskites, to achieve excellent performance of the TMD-based photodetectors. Significantly, the interfacial charge transfer from the CsPbBr to the MoS layer has been evidenced by the observed photoluminescence quenching and shortened decay time of the hybrid MoS/CsPbBr. Resultantly, such a hybrid MoS/CsPbBr photodetector exhibits a high photoresponsivity of 4.4 A/W, an external quantum efficiency of 302%, and a detectivity of 2.5 × 10 Jones because of the high efficient photoexcited carrier separation at the interface of MoS and CsPbBr. The photoresponsivity of this hybrid device presents an improvement of 3 orders of magnitude compared with that of a MoS device without CsPbBr. The response time of the device is also shortened from 65.2 to 0.72 ms after coupling with MoS layers. The combination of the all-inorganic perovskite layer with high photon absorption and the carrier transport TMD layer may pave the way for novel high-performance optoelectronic devices.

Excitonic solar cells (XSCs) have attracted tremendous attentions due to their high solar-to-electric power conversion efficiency (PCE). However, to further improve the PCE of XSC, finding an efficient donor material with both suitable direct bandgap and high carrier mobility is still a great challenge. Here, we report a black arsenic-phosphorus monolayer as highly efficient donor for XSCs based on first-principle calculations. Firstly, monolayer arsenic-phosphorus polymorphs with α, β, γ, δ, and ε phases were built, among which α−AsP and β−AsP have been verified to be thermodynamically stable. Significantly, monolayer α−AsP possesses a direct bandgap with energy of 1.54 eV, which covers the main energy of solar spectrum. Moreover, its electronic mobility is as high as 14,380 cm 2 V-1 s-1 , which is much higher than silicon. These two crucial merits made it a promising candidate as donor materials for XSC device and the theoretical simulations demonstrate a maximum PCE of 22.1% for the primarily designed α−AsP/GaN XSC. Interestingly, the suitable electronic structure of α−AsP enables a formation of perfect type-II semiconductor heterojunction with GaN, which will boost the separation and transport of photogenerated carriers with the assistance of built-in field and high mobility. Particularly, α phase few-layer material of arsenic-phosphorus alloy has been experimentally synthesized recently, which paves the way for experimental realization of black arsenic-phosphorus monolayer donor.