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.

Zinc oxide (ZnO) is considered as an ideal candidate for ultraviolet (UV) lasers due to its unique advantages of wide direct bandgap and large exciton binding energy. Recently, whispering-gallery mode (WGM) lasing has attracted considerable attention for its high quality factor and low lasing threshold. The corresponding investigations have very important significance not only for fundamental scientific research but also for the potential applications in short-wavelength optoelectronic devices. In this paper, progress in ZnO microlasers is reviewed systematically. The fabrication methods for ZnO WGM microcavities are introduced first. Then the characteristics of single-photon and multiphoton pumped WGM lasing are presented. The lasing mechanisms on excitonic, electron-hole plasma and exciton-polariton lasing are reviewed in detail. Finally, recent advances in ZnO-based microlaser devices such as heterojunction laser diodes are explored. The further research challenges and some strategies are also indicated for the promising applications.

A facile hydrothermal strategy to synthesize sulfur-doped reduced graphene oxide (S-RGO) sheets with good conductivity is proposed by using only graphene oxide (GO) sheets and sodium sulphide (Na2S) as precursors through a hydrothermal reaction process at 200 °C in one pot. The introduced Na2S can act as not only a sulfur dopant, but also as a highly efficient reducing agent in the formation of S-RGO sheets, which dramatically improves the electrical conductivities of the resulting S-RGO sheets compared with previous reports. The current reaches about 50.0 mA at an applied bias of 2.0 V for the optimized sample with 2.22 at% sulfur doping. This current value is much higher than that of RGO sheets (∼1.2 mA) annealed at 200 °C, and very close to that of single-layer graphene sheets (∼68.0 mA) prepared using chemical vapor deposition under the same test conditions. The resulting highly conductive S-RGO sheets offer many promising technological applications such as efficient metal-free electrocatalysts in oxygen reduction reactions in fuel cells and as supercapacitor electrode materials for high-performance Li-ion batteries.

An Ag/ZnO microrod/Ag ultraviolet photodetector is fabricated, the ZnO microrod shows a hexagonal whispering gallery cavity structure. Upon a 325 nm ultraviolet illumination, the device shows a high sensitivity of 4 × 10(4) A/W and a high photocurrent gain of 1.5 × 10(5) at 5 V bias. Under different illumination power P, the photocurrent Ilight obeys a power law relation Ilight ∝ P(0.69). The high performance is probably attributed to a Schottky barrier at Ag/ZnO interface and optical whispering gallery mode effect in the ZnO microrod.

Four configurations of whispering-gallery-mode (WGM) microcavities were designed and fabricated to modulate the optically pumped lasing characteristics by polymer modification on hexagonal ZnO microrod surfaces. On the basis of the total internal reflection (TIR) at the boundary of microcavities, the lasing characteristics were improved by raising the relative refractive index. Considering the different reflective conditions at various side surfaces, the typical lasing mode equation for whispering-gallery microcavity was modified to adapt for general situation even with unsymmetrical structure, and then employed to discuss the observed lasing behaviors, in the polyvinylcarbazole (PVK) modified ZnO microrods, such as mode position, mode numbers and quality factor. The optical field distributions for TE modes of the four configurations were also simulated by 2-dimensional finite difference time-domain (FDTD) method. The simulation agreed well with the experimental results to support the resonance mechanism.