A tapping-mode tuning fork force-sensing method for near-field scanning optical microscope is reported. Use of the tapping-mode tuning fork with mechanically asymmetric excitation generates better stability and sensitivity than in the shear force mode. Comparison of force curves for the two methods demonstrate that the tapping-mode tuning fork method provides a simpler and more sensitive method for near-field measurements. The method is demonstrated by imaging a sample consisting of 500 nm standard polystyrene spheres on silica in both air and water.

Metal phosphorous tri-chalcogenides are a category of new ternary 2D layered materials with a wide range of tuneable bandgaps (1.2-3.5 eV). These wide-bandgap semiconductors exhibit great potential applications in solar-blind ultraviolet (SBUV) photodetection. However, these 2D solarblind photodetectors suffer from low photoresponsivity, slow photoresponse speed, and narrow operation spectral region, thereby limiting their practical applications. Here, an ultra-broadband photodetection based on a FePSe 3 / MoS 2 heterostructure with coverage ranging from solar-blind ultraviolet 265 nm to longwave infrared (LWIR) 10.6 µm is reported. Notably, the device exhibits excellent weak light detection capability. A high photoresponsivity of 33 600 A W −1 and an external quantum efficiency of 1.57 × 10 7 % are demonstrated. A noise-equivalent power as low as 5.7 × 10 -16 W Hz −1/2 and a specific detectivity up to 1.51 × 10 13 cm Hz 1/2 W −1 are realized in the SBUV region. The room temperature LWIR photoresponsivity of 0.12 A W −1 is realized. This work opens a route to design high-performance SBUV photo detectors and wide spectral photoresponse applications.

Lead‐free Cs2AgBiBr6 double perovskite is considered to be a promising alternative to the traditional lead‐based analogues due to its long carrier lifetime, high structural stability, and non‐toxicity. However, the large band gap limits its absorption of visible light, which is not conducive to further optoelectronic applications. Herein, a thermochromic strategy is reported to decrease the band gap of Cs2AgBiBr6 by approximately 0.36 eV, obtaining the smallest reported band gap of 1.69 eV under ambient conditions. The experimental data indicate that after annealing the Cs2AgBiBr6 single crystals at 400 °C, the silver (Ag) and bismuth (Bi) atoms occupy the B‐site in a random way and form a partially disordered configuration. The formation of the antisite defects broadens the band edges and decreases the band gap. This work offers new insights into the preparation of narrow band gap lead‐free double perovskites, and a deep understanding of their structural and electronic properties for further development in photoelectric devices.

Their nanoscale size endows perovskite quantum dots (QDs) with processing flexibility and high tunability of optoelectronic properties. The vast surface area also provides an opportunity for ligand engineering to offer QDs extra protection, which however, will impede charge transport in the QD array. Currently, the surface treatments that can balance both stability and conductivity of the perovskite QD array remain a huge challenge. Here, we report in situ growth of an atomic guanidinium lead iodide perovskite matrix on CsPbI 3 QDs. In addition to the effect of trap passivation, the matrix can also provide substantial surface strain to improve the QD phase stability. Meanwhile, the ultrathin matrix allows efficient coupling and charge transport in the QD solids. As a result, the CsPbI 3 QD solar cells can achieve both superior device stability and performance. We believe the development of a multifunctional surface matrix will become one of the future research focuses in perovskite QD-based devices.

Organometal halide perovskite nanocrystals show near-unity photoluminescence quantum yield which decrease dramatically in thin films because of nonradiative losses. Here, we demonstrate a solution-processed highly luminescent perovskite film by confining the MAPbBr3 nanocrystals into the inorganic CaBr2 matrix in situ. The confinement of the exciton in small nanograins facilitates radiative recombination. Meanwhile, part of the lattice-incorporated calcium ions could alter the electronic band structures and then increase the exciton binding energy of MAPbBr3 perovskite. The synergism of morphology control and structural regulation leads to efficient radiative recombination and the enhancement of photoluminescence quantum yield from 4.2% to 45.6%. Moreover, the chloride could also be introduced and stabilized into the perovskite lattice through the calcium incorporation. Desirable pure blue (<480 nm) emission was obtained in situ through manipulating the calcium and chloride ions in the precursor solutions without the assistance of bulky ligands. Our strategies of locally creating luminescent color-tunable perovskite films are promising for further improving the performance of organic–inorganic hybrid perovskite electroluminescence devices.