Yibin Yang

The intrinsic B-site antisite defects fundamentally constrain the performance of double halide perovskites Cs₂AgBiCl₆ and Cs₂AgInCl₆.

The separation of photogenerated electron–hole pairs is crucial for the construction of high-performance and wide-band responsive photodetectors. The type-I heterojunction as a photodetector is seldomly studied due to its limited separation of the carriers and narrow optical response. In this work, we demonstrated that the high performance of type-I heterojunction as a broadband photodetector can be obtained by rational design of the band alignment and proper modulation from external electric field. The heterojunction device is fabricated by vertical stacking of non-layered MnS and WSe₂ flakes. Its type-I band structure is confirmed by the first-principles calculations. The MnS/WSe₂ heterojunction presents a wide optical detecting range spanning from 365 nm to 1550 nm. It exhibits the characteristics of bidirectional transportation, a current on/off ratio over 10³, and an excellent photoresponsivity of 108 A W⁻¹ in the visible range. Furthermore, the response time of the device is 19 ms (rise time) and 10 ms (fall time), which is much faster than that of its constituents MnS and WSe₂. The facilitation of carrier accumulation caused by the interfacial band bending is thought to be critical to the photoresponse performance of the heterojunction. In addition, the device can operate in self-powered mode, indicating a photovoltaic effect.

An inverse opal structure of SnO₂ with a honeycomb morphology is introduced as the framework for the attached perovskite materials and functional layers in the hybrid perovskite-based solar cells simultaneously. Three different pore sizes of polystyrene microsphere layers, with diameters of 350, 480, and 600 nm, were fabricated through a vertical self-assembly vaporization technique. The polystyrene (PS) layer served as the sacrificial template for the inverse opal structure. By controlling the spinning parameters, the inverse opal-structured SnO₂ layer was used to constrain them into a single-layer stacking structure. These layers with varying pore sizes were subsequently applied onto a dense electron transport layer that is in contact with the perovskite layer. A carbon electrode is used as photovoltaic solar cells. The major benefits of this approach were systematically analyzed through structural characterizations and various means. The semiphotonic crystal layer induces modulation effects, resulting in increased light absorption and surface area, which leads to a substantial increase in short-circuit density. By studying the electrochemical properties in the dark to exclude the influence of optical effects, we attribute the slight increase in the fill factor to the increased surface area, which enhances carrier transport. Among the different layers, the inverse opal layer prepared with 480 nm polystyrene microspheres displayed superior photovoltaic performance parameters due to its appropriate surface area and relatively higher light absorption. The power conversion efficiency of the MAPbI₃ perovskite solar cell showed a relative enhancement of 55%. Additionally, aging tests demonstrated that devices with the additional structural layer exhibited good endurance under conventional atmospheric conditions after 1440 h of aging.

Due to its good p-type semiconductor characteristics, MnSe has a great application prospect in high-performance electronic and optoelectronic devices. However, heterojunctions of MnSe still need to be deeply studied to improve its electrical and photoelectric properties. Here, it is reported that the two-dimensional (2D) MnSe/WSe₂ heterojunction is structured by the non-layered MnSe nanosheets synthesized by chemical vapor deposition (CVD) method and the mechanically exfoliated layered WSe₂. The heterojunction device exhibits a rectification effect and a current on/off ratio of 6,557. Meanwhile, it has a broad spectral range response from ultraviolet (UV) to short-wave infrared radiation (SWIR) (300–2,200 nm), and achieves an ultra-high responsivity of 156 A/W, along with an excellent detectivity of 2.21 × 10¹² jones, and an outstanding external quantum efficiency (EQE) of 36,400%. Moreover, the type II band alignment and the built-in potential in the MnSe/WSe₂ heterojunction can facilitate the separation of the photoexcited electron-hole pairs, which enables the significant photovoltaic characteristics and self-powered photoswitching response. This work reveals the novel performance of the 2D MnSe/WSe₂ heterojunction and a great potential in photoswitching, photodetector, and photovoltaic applications.

A photovoltaic photodetector based on a hybrid dimensional WSe₂/WS₂/p-Si dual-vdW heterojunction is constructed, which can realize the coupling of the photovoltaic effect and photogating effect.

Ti₃C₂T_x QDs were prepared and the QDs/PVA film was exploited as a saturable absorber. Both Q-switched and mode-locked operations based on the SA were easily achieved. The SA showed long-term stability in ultrafast photonic applications for 12 months.

The effects of elemental tellurium doping and decorating on the photoluminescence quantum yield (PL QY) and the environmental stability of the CsPbBr₃ quantum dots (QDs) have been systematically studied. The PL spectra blue-shifts from 520 to 464 nm gradually with the increase in the amount of Te, and the full width at half-maximum (FWHM) increases from 20 to 62 nm and decreases to 27 nm accordingly. The morphology of the untreated samples has a rectangular shape with distinct boundaries, whereas the Te-doped samples have a semi-core-shell structure with partially coated CsPb₂Br₅ after tellurium doping. Furthermore, the apparent size of the nanocomposites increases to 20 nm, but the crystal size of the core decreases slightly according to the broadened peaks of X-ray diffraction (XRD). Further investigation by X-ray photoelectron spectroscopy shows that the binding energy of Pb-Br increases and Pb-Te bonds are formed in Te-doped samples, which can enhance the stability of QDs from the view of strengthening the chemical bonds and inhibiting the detaching behavior of bromine under moisture. At the nominal content of Pb/Te = 1:0.4, the thermal decomposition temperature of the QDs increases from 300 to 500 °C; the maximum of PL QY increases to 70% for the 1:0.4 sample and the relative PL peak intensity maintains 50% of the initial value after a 60 h aging simulation. Finally, the nanocomposite materials are fabricated into a white light-emitting device (WLED). Under the illumination of a commercial GaN chip, the device shows a good Commission Internationale de lEclairage (CIE) color coordination of (0.3291,0.3318).