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The present work reports highly efficient flexible and reabsorption-free scintillators based on two zero-dimensional (0D) organic copper halides (TBA)CuX2 (TBA = tetrabutylammonium cation; X = Cl, Br). The (TBA)CuX2 exhibit highly luminescent green and sky-blue emissions peaked at 510 and 498 nm, with large Stokes shifts of 224 and 209 nm and high photoluminescence quantum yields (PLQYs) of 92.8% and 80.5% at room temperature for (TBA)CuCl2 and (TBA)CuBr2 single crystals (SCs), respectively. Interestingly, above room temperature, their PLQYs increase with temperature and reach near unity at 320 and 345 K for (TBA)CuCl2 and (TBA)CuBr2, respectively. The excellent properties originate from self-trapped excitons (STEs) in individual [CuX2]- quantum rods, which is demonstrated by the temperature-dependent PL, ultrafast transient absorption (TA) combined with density functional theory (DFT) calculations. The (TBA)CuX2 scintillators show bright radioluminescence (RL), impressive linear response to dose rate in a broad range, and high light yields. Their potential application in X-ray imaging is demonstrated by using (TBA)CuX2 composite scintillation screens. Importantly, flexible scintillators are demonstrated to be superior than flat ones for imaging nonplanar objects by conformally coating, which produce accurate images with negligible distortion.

Black phase CsPbI3 perovskites have emerged as one of the most promising materials for use in optoelectronic devices due to their remarkable properties. However, black phase CsPbI3 usually possesses poor stability and involves a phase change process, resulting in an undesired orthorhombic (δ) yellow phase. Here, the enhanced stability of CsPbI3 nanocrystals is achieved by incorporating the Cu2+ ion into the CsPbI3 lattice under mild conditions. In particular, the Cu2+-doped CsPbI3 film can maintain red luminescence for 35 days in air while the undoped ones transformed into the nonluminescent yellow phase in several days. Furthermore, first-principles calculations verified that the enhanced stability is ascribed to the increased formation energy due to the successful doping of Cu2+ in CsPbI3. Benefiting from such an effective doping strategy, the as-prepared Cu2+-doped CsPbI3 as an emitting layer shows much better performance compared with that of the undoped counterpart. The turn-on voltage of the Cu2+-doped quantum-dot light-emitting diode (QLED) (1.6 V) is significantly reduced compared with that of the pristine QLED (3.8 V). In addition, the luminance of the Cu2+-doped QLED can reach 1270 cd/m2, which is more than twice that of the pristine CsPbI3 QLED (542 cd/m2). The device performance is believed to be further improved by optimizing the purification process and device structure, shedding light on future applications.

We systematically studied the ability of 20 alkali halides to form solid hydrates in the frozen state from their aqueous solutions by terahertz time-domain spectroscopy combined with density functional theory (DFT) calculations. We experimentally observed the rise of new terahertz absorption peaks in the spectral range of 0.3-3.5 THz in frozen alkali halide solutions. The DFT calculations prove that the rise of observed new peaks in solutions containing Li+, Na+, or F- ions indicates the formation of salt hydrates, while that in other alkali halide solutions is caused by the splitting phonon modes of the imperfectly crystallized salts in ice. As a simple empirical rule, the correlation between the terahertz signatures and the ability of 20 alkali halides to form a hydrate has been established.

0D–2D mixed-dimensional hybrid structures, which combine tunable optical properties of 0D quantum dots (QDs) and high transport mobilities of 2D layered materials, have shown great potential in opt...

Black phase CsPbI

0D-2D mixed-dimensional hybrid structures, which combine tunable optical properties of 0D quantum dots (QDs) and high transport mobilities of 2D layered materials, have shown great potential in optoelectronic applications. Understanding charge transfer dynamics at the 0D-2D interface is essential but still lacking. Here, using PbS QD/WSe

Decreasing the variability in quantum dot (QD) syntheses is desirable for better uniformity of samples for use in QD-based studies and applications. Here we report a highly reproducible linear relationship between the concentration of ligand (in this case oleic acid, OA) and the lowest energy exciton peak position (nm) of the resulting PbS QDs for various hot-injection temperatures. Thus, for a given injection temperature, the size of the PbS QD product is purely controlled by the amount of OA. We used this relationship to study PbS QD solar cells that are fabricated from the same size of PbS QDs but synthesized using four different injection temperatures: 95, 120, 150, and 185 °C. We find that the power conversion efficiency does not depend on injection temperature but that the V(oc) is higher for QDs synthesized at lower temperatures while the J(sc) is improved in higher temperature QDs.

Two-dimensional Ruddlesden–Popper type perovskites (2D perovskites) have recently attracted increasing attention. It is expected that 2D perovskite-based heterostructures can significantly improve the efficiency of the optoelectronic devices and extend the material functionalities; however, rational synthesis of such heterostructures has not been realized to date. We report on a general low-temperature synthetic strategy for the synthesis of 2D perovskite-based lateral and vertical (n-CH3(CH2)3NH3)2PbI4/(n-CH3(CH2)3NH3)2(CH3NH3)Pb2I7 heterostructures for the first time. A combination of solution synthesis and gas–solid phase intercalation approach allows us to efficiently synthesize both lateral and vertical heterostructures with great flexibility. X-ray diffraction, photoluminescence, and photoluminescence excitation mapping and electrical transport measurement studies reveal the successful synthesis of lateral and vertical heterostructures with precisely spatial-modulation control and distinguishable in...