Search

Ultrathin flat lenses based on metasurfaces or metamaterials have shown great promise in recent years as essential components in nano-optical system, with capability of abrupt changes of light wavefronts. However, such structural designs require complex nanopatterns and a time-consuming nanofabrication process. In this regard, flat lenses are developed based on 2D perovskite nanosheets, using a cost-effective mask-free femtosecond direct laser writing system. The optical properties of the 2D perovskite are rationally adjusted through facile composition engineering as well as thickness-dependent quantum-size confinement. A diffraction theory model is derived to understand the focusing mechanism of the 2D perovskite nanosheets flat lenses. The as-fabricated lenses exploit the tunable material property variations to effectively manipulate not only the amplitude but also the phase of the incident light to focus into a 3D focal spot with a sub-wavelength resolution in the range of 0.5-0.9λ. The results pave the way toward low-cost and large-scale high-resolution imaging applications in the future.

Metal halide perovskites represent a family of the most promising materials for fascinating photovoltaic and photodetector applications due to their unique optoelectronic properties and much needed simple and low-cost fabrication process. The high atomic number (Z) of their constituents and significantly higher carrier mobility also make perovskite semiconductors suitable for the detection of ionizing radiation. By taking advantage of that, the direct detection of soft-X-ray-induced photocurrent is demonstrated in both rigid and flexible detectors based on all-inorganic halide perovskite quantum dots (QDs) synthesized via a solution process. Utilizing a synchrotron soft-X-ray beamline, high sensitivities of up to 1450 µC Gyair-1 cm-2 are achieved under an X-ray dose rate of 0.0172 mGyair s-1 with only 0.1 V bias voltage, which is about 70-fold more sensitive than conventional α-Se devices. Furthermore, the perovskite film is printed homogeneously on various substrates by the inexpensive inkjet printing method to demonstrate large-scale fabrication of arrays of multichannel detectors. These results suggest that the perovskite QDs are ideal candidates for the detection of soft X-rays and for large-area flat or flexible panels with tremendous application potential in multidimensional and different architectures imaging technologies.