All-inorganic perovskites nanostructures, such as CsPbCl 3 nanocrystals (NCs), are promising in many applications including light-emitting diodes, photovoltaics, and photodetectors. Despite the impressive performance that was demonstrated, a critical issue remains due to the instability of the perovskites in ambient. Herein, we report a method of passivating crystalline CsPbCl 3 NC surfaces with 3-mercaptopropionic acid (MPA), and superior ambient stability is achieved. The printing of these colloidal NCs on the channel of graphene field-effect transistors (GFETs) on solid Si/SiO 2 and flexible polyethylene terephthalate substrates was carried out to obtain CsPbCl 3 NCs/GFET heterojunction photodetectors for flexible and visible-blind ultraviolet detection at wavelength below 400 nm. Besides ambient stability, the additional benefits of passivating surface charge trapping by the defects on CsPbCl 3 NCs and facilitating highefficiency charge transfer between the CsPbCl 3 NCs and graphene were provided by MPA. Extraordinary optoelectronic performance was obtained on the CsPbCl 3 NCs/graphene devices including a high ultraviolet responsivity exceeding 10 6 A/W, a high detectivity of 2 × 10 13 Jones, a fast photoresponse time of 0.3 s, and ambient stability with less than 10% degradation of photoresponse after 2400 h. This result demonstrates the crucial importance of the perovskite NC surface passivation not only to the performance but also to the stability of the perovskite optoelectronic devices.

In ZnO quantum dot/graphene heterojunction photodetectors, fabricated by printing quantum dots (QDs) directly on the graphene field-effect transistor (GFET) channel, the combination of the strong quantum confinement in ZnO QDs and the high charge mobility in graphene allows extraordinary quantum efficiency (or photoconductive gain) in visible-blind ultraviolet (UV) detection. Key to the high performance is a clean van der Waals interface to facilitate an efficient charge transfer from ZnO QDs to graphene upon UV illumination. Here, we report a robust ZnO QD surface activation process and demonstrate that a transition from zero to extraordinarily high photoresponsivity of 9.9 × 10 A/W and a photoconductive gain of 3.6 × 10 can be obtained in ZnO QDs/GFET heterojunction photodetectors, as the ZnO QDs surface is systematically engineered using this process. The high figure-of-merit UV detectivity D* in exceeding 1 × 10 Jones represents more than 1 order of magnitude improvement over the best reported previously on ZnO nanostructure-based UV detectors. This result not only sheds light on the critical role of the van der Waals interface in affecting the optoelectronic process in ZnO QDs/GFET heterojunction photodetectors but also demonstrates the viability of printing quantum devices of high performance and low cost.

The significant relationships found between the three exercise tests, and the regression equations predicting peak work rate on the CET from the 6MWT or the ISWT, may allow for the estimation of intensity of cycle exercise training from walk tests in COPD patients.

Graphene field effect transistor sensitized by a layer of semiconductor (sensitizer/GFET) is a device structure that is investigated extensively for ultrasensitive photodetection. Among others, organometallic perovskite semiconductor sensitizer has the advantages of long carrier lifetime and solution processable. A further step to improve the responsivity is to design a structure that can promote electron-hole separation and selective carrier trapping in the sensitizer. Here, the use of a hybrid perovskite-organic bulk heterojunction (BHJ) as the light sensitizer to achieve this goal is demonstrated. Our spectroscopy and device measurements show that the CH 3 NH 3 PbI 3 -PCBM BHJ/GFET device has improved charge separation yield and carrier lifetime as compared to a reference device with a CH 3 NH 3 PbI 3 sensitizer only. The key to these enhancement is the presence of [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM), which acts as charge separation and electron trapping sites, resulting in a 30-fold increase in the photoresponsivity. This work shows that the use of a small amount of electron or hole acceptors in the sensitizer layer can be an effective strategy for improving and tuning the photoresponsivity of sensitizer/GFET photodetectors.

Suspended single-wall carbon nanotube (SWCNT) thin film bolometers have been fabricated on microchannels patterned on Si substrates using electron-beam lithography. The much improved bolometric photoresponse is attributed to the reduced thermal link between SWCNT bolometer and substrate, which can be controlled by tuning the width and spacing of the microchannels. The detectivity D∗ up to 4.5×105 cm Hz1/2/W has been obtained at room temperature, which is at least five times better than that of the unsuspended counterpart and may be further improved via elimination of metallic SWCNTs and improvement of the charge and heat transport across the intertube junctions.