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Real‐time in vivo detection of cancer via attenuation‐based plain X‐ray imaging is proposed to fundamentally overcome the penetration depth limits of current fluorescence‐based imaging techniques. Using cesium lead bromide (CsPbBr3, CPB) quantum dot (QD) scintillators, real‐time X‐ray detection of 5 mm‐sized Panc‐1 cell tumors grown in a mouse is successfully performed. The QDs are rapidly co‐synthesized and double‐encapsulated with silicon dioxide (SiO2) to completely prevent them from being aggregated, decomposed, or released; they are then conjugated with antibodies to target pancreatic cancer. Due to the dramatic X‐ray attenuation, the X‐ray signal from the CPB QDs placed under the 2 cm‐thick tissue is clearly observed, while their fluorescence signal is not detected at all. In in vivo mouse experiments, the injection of a tiny amount (2.8 μg on a QD basis) of the CPB–SiO2@SiO2–Ab nanoparticles gives rise to a bright spot at the location of the tumor. Cell viability assay and histological analysis confirm the biocompatibility and nontoxicity of the nanoparticles. [ABSTRACT FROM AUTHOR]

Inverted structure heterojunction colloidal quantum dot (CQD) photovoltaic devices with an improved performance are developed using single-step coated CQD active layers with a thickness of ≈60 nm. This improved performance is achieved by managing the device architecture to simultaneously enhance charge generation and extraction by raising optical absorption within the depletion region. The devices are composed of an ITO/PEDOT:PSS/PbS-CQD/ZnO/Al structure, in which the p-n heterojunction is placed at the rear (i.e., opposite to the side of illumination) of the devices (denoted as R-Cell). Sufficient optical generation is achieved at very low CQD layer thicknesses of 45-60 nm because of the constructive interference caused by the insertion of ZnO between the CQD and the Al electrode. The power conversion efficiency (PCE) of R-Cells containing a thin CQD layers (≈60 nm) is much higher (≈6%) than that of conventional devices containing CQD layers with a thickness of ≈300 nm (PCE ≈4.5%). This optical management strategy provides a general guide to obtain the optimal trade-off between generation and extraction in planar p-n junction solar cells. In terms of device engineering, all the layers in our R-Cells are fabricated using single coating, which can lead to compatibility with high-throughput processes. [ABSTRACT FROM AUTHOR]