We realized photovoltaic operation in large-scale MoS2 monolayers by the formation of a type-II heterojunction with p-Si. The MoS2 monolayer introduces a built-in electric field near the interface between MoS2 and p-Si to help photogenerated carrier separation. Such a heterojunction photovoltaic device achieves a power conversion efficiency of 5.23%, which is the highest efficiency among all monolayer transition-metal dichalcogenide-based solar cells. The demonstrated results of monolayer MoS2/Si-based solar cells hold the promise for integration of 2D materials with commercially available Si-based electronics in highly efficient devices.

This study describes a strategy for developing ultra-high-responsivity broadband Si-based photodetectors (PDs) using ZnO nanorod arrays (NRAs). The ZnO NRAs grown by a low-temperature hydrothermal method with large growth area and high growth rate absorb the photons effectively in the UV region and provide refractive index matching between Si and air for the long-wavelength region, leading to 3 and 2 orders of magnitude increase in the responsivity of Si metal-semiconductor-metal PDs in the UV and visible/NIR regions, respectively. Significantly enhanced performances agree with the theoretical analysis based on the finite-difference time-domain method. These results clearly demonstrate that Si PDs combined with ZnO NRAs hold high potential in next-generation broadband PDs.

We demonstrate solar-blind photodetectors (PDs) by employing AlN thin films on Si(100) substrates with excellent temperature tolerance and radiation hardness. Even at a bias higher than 200 V the AlN PDs on Si show a dark current as low as ~ 1 nA. The working temperature is up to 300°C and the radiation tolerance is up to 1013 cm−2 of 2-MeV proton fluences for AlN metal-semiconductor-metal (MSM) PDs. Moreover, the AlN PDs show a photoresponse time as fast as ~ 110 ms (the rise time) and ~ 80 ms (the fall time) at 5 V bias. The results demonstrate that AlN MSM PDs hold high potential in next-generation deep ultraviolet PDs for use in harsh environments.

Organic semiconductors demonstrate several advantages over conventional inorganic materials for novel electronic and optoelectronic applications, including molecularly-tunable properties, flexibility, low-cost, and facile device integration. However, before organic semiconductors can be used for the next generation of devices, such as ultrafast photodetectors (PDs), it is necessary to develop new materials that feature both high mobility and ambient stability. Toward this goal, we demonstrate a highly stable PD based on organic single crystal [PtBr2(5,5′-bis(CF3CH2OCH2)-2,2′-bpy)] (or "Pt complex (1o)") as the active Revised Manuscript Furthermore, the device features a maximum photoresponsivity of 1×10 3 A/W, a detectivity of 1.1×10 12 cm Hz-1/2 W-1 at 5 V, and a record fast response/recovery time of 80/90 μs, which has never been previously achieved in other organic PDs. Our findings strongly support and promote the use of single crystal Pt complex (1o) in the next generation of organic optoelectronic devices.

Despite great improvements in traditional inorganic photodetectors and photovoltaics, more progress is needed in the detection/collection of light at low-level conditions. Traditional photodetectors tend to suffer from high noise when operated at room temperature; therefore, these devices require additional cooling systems to detect weak or dim light. Conventional solar cells also face the challenge of poor light-harvesting capabilities in hazy or cloudy weather. The real world features such varying levels of light, which makes it important to develop strategies that allow optical devices to function when conditions are less than optimal. In this work, we report an organic/inorganic hybrid device that consists of graphene quantum dot-modified poly(3,4-ethylenedioxythiophene) polystyrenesulfonate spin-coated on Si for the detection/harvest of weak light. The hybrid configuration provides the device with high responsivity and detectability, omnidirectional light trapping, and fast operation speed. To demonstrate the potential of this hybrid device in real world applications, we measured near-infrared light scattered through human tissue to demonstrate noninvasive oximetric photodetection as well as characterized the device's photovoltaic properties in outdoor (i.e., weather-dependent) and indoor weak light conditions. This organic/inorganic device configuration demonstrates a promising strategy for developing future high-performance low-light compatible photodetectors and photovoltaics.

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Surface plasmon (SP) mediated emission from ZnO nanorod arrays (NRAs)/Ag/Si structures has been investigated. The ratio of visible emission to UV emission can be increased by over 30 times via coupling with SP without deterioration of the crystal quality. The fact that the effect of SP crucially depends on the size of Ag island films provides the feasibility to significantly enhance the yellow-green emission of the ZnO nanostructures without sacrificing the crystallinity of ZnO.