A graphene/n-type silicon (n-Si) heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity, which can be utilized for the development of high-performance photodetectors. However, graphene/n-Si heterojunction photodetectors reported previously suffer from relatively low specific detectivity due to large dark current. Here, by introducing a thin interfacial oxide layer, the dark current of graphene/n-Si heterojunction has been reduced by two orders of magnitude at zero bias. At room temperature, the graphene/n-Si photodetector with interfacial oxide exhibits a specific detectivity up to 5.77 × 10(13) cm Hz(1/2) W(-1) at the peak wavelength of 890 nm in vacuum, which is highest reported detectivity at room temperature for planar graphene/Si heterojunction photodetectors. In addition, the improved graphene/n-Si heterojunction photodetectors possess high responsivity of 0.73 A W(-1) and high photo-to-dark current ratio of ≈10(7) . The current noise spectral density of the graphene/n-Si photodetector has been characterized under ambient and vacuum conditions, which shows that the dark current can be further suppressed in vacuum. These results demonstrate that graphene/Si heterojunction with interfacial oxide is promising for the development of high detectivity photodetectors.

In the last few decades, advances and breakthroughs of carbon materials have been witnessed in both scientific fundamentals and potential applications. The combination of carbon materials with traditional silicon semiconductors to fabricate solar cells has been a promising field of carbon science. The power conversion efficiency has reached 15-17% with an astonishing speed, and the diversity of systems stimulates interest in further research. Here, the historical development and state-of-the-art carbon/silicon heterojunction solar cells are covered. Firstly, the basic concept and mechanism of carbon/silicon solar cells are introduced with a specific focus on solar cells assembled with carbon nanotubes and graphene due to their unique structures and properties. Then, several key technologies with special electrical and optical designs are introduced to improve the cell performance, such as chemical doping, interface passivation, anti-reflection coatings, and textured surfaces. Finally, potential pathways and opportunities based on the carbon/silicon heterojunction are envisaged. The aspects discussed here may enable researchers to better understand the photovoltaic effect of carbon/silicon heterojunctions and to optimize the design of graphene-based photodevices for a wide range of applications.

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Piezochromic fluorescent (PCF) materials with distinct multicolor switching have attracted wide attention in many fields such as optoelectronic devices and deformation detection. However, few PCF materials with low-pressure stimuli and good recoverability have been reported. A highly sensitive and easily recoverable PCF molecular system that can switch between green (G) and orange (O) emissions upon an extremely low piezoresponsive (PR) of 0.5 MPa and heating at 120 °C is demonstrated. A mechanistic study combining X-ray diffraction analysis and the theoretical calculations reveal that a slight change in slipping-angle of π-stacks induced by mechanical pressure amplifies the exciton couplings from G to O J-aggregates, leading to not only distinct PCF switching but also high emission efficiencies >0.5 owing to superradiance of J-aggregate excitons. Benefiting from low MPa PR, high emission efficiency, and good recoverability applications including haptic sensors and anti-counterfeiting application are demonstrated. This research introduces the effect of stimuli-responsive excitonic coupling as new design guidance for developing PCF materials with low-pressure stimuli, high emission efficiency, and good recoverability.