Perovskite quantum dots are emerging as attractive materials for photonic and optoelectronic applications. Patterning is an important step to incorporate them into display, anti‐counterfeiting, and optical chip applications. In this work, an in situ inkjet printing strategy is demonstrated for fabricating perovskite quantum dots patterns by printing perovskite precursor solutions onto a polymeric layer. Importantly, this strategy can achieve bright photoluminescence with a quantum yield up to 80% and shows broad applicability to a variety of perovskites and polymers. Moreover, the as‐fabricated perovskite quantum dots patterns are composed of a microdisks array on the surface of polymeric layer. The size of these microdisks can be varied by adjusting the printing temperature. To demonstrate the potential use in display and advanced anti‐counterfeiting applications, color pixel patterns and 2D code pattern are fabricated by varying the precursor solutions. The combination of superior photoluminescence properties, simple process, and low cost makes the in situ inkjet printing strategy very promising for patterning perovskite quantum dots toward photonic integrations.

Perovskite quantum dots have been attractive building blocks for novel photonic devices development, where patterning is usually one of the most critical steps. We report on the combination of in situ fabrication and direct laser writing based on a 405 nm nanosecond laser, which provides an efficient and simple scheme for patterning perovskite quantum dots during the formation process. The as-fabricated gamma phase CsPbI3 quantum dots patterns show bright photoluminescence emission with a quantum yield up to 92%. By varying the key parameters of the direct laser writing, a minimum line width of 900 nm was achieved. A light-emitting optical grating with a period of 4 μm was fabricated and its polarization and structural color characteristics were discussed. The reported approach offers a route for fabricating patterned perovskite quantum dots with designed structures for photonic applications including micro-LED display, anticounterfeiting, and nanolasers.

Room-temperature-operated continuous-wave lasers have been intensively pursed in the field of on-chip photonics. The realization of a continuous-wave laser strongly relies on the development of gain materials. To date, there is still a huge gap between the current gain materials and commercial requirements. In this work, we demonstrate continuous-wave lasers at room temperature using rationally designed in situ fabricated perovskite quantum dots in polyacrylonitrile films on a distributed feedback cavity. The achieved threshold values are 15, 24, and 58 W/cm 2 for green, red, and blue lasers, respectively, which are one order lower than the reported values for the conventional CdSe quantum dot-based continuous-wave laser. Except for the high photoluminescence quantum yields, smooth surface, and high thermal conductivity of the resulting films, the key success of an ultralow laser threshold can be explained by the interaction of polyacrylonitrile and perovskite induced "charge spatial separation" effects. This progress opens up a door to achieve on-chip continuous-wave lasers for photonic applications.

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In this work, the integration of in situ fabricated perovskite quantum dots embedded composite films (PQDCFs) as downshifting materials is first reported for enhancing the ultraviolet (UV) response of silicon (Si) photodetectors toward broadband and solar‐blind light detection. External quantum efficiency measurements show that the UV response of PQDCF coated Si photodiodes greatly improves from near 0% to at most of 50.6% ± 0.5% @ 290 nm. As compared to the calculated maximum value of 87%, the light coupling efficiency of the integrated device is determined to be 80%@395 nm, suggesting an efficient downshifting process. Furthermore, PQDCF is also successfully adapted for electron multiplying charge coupled device (EMCCD) based image sensor. The PQDCF coated EMCCD shows linear response with high‐resolution imaging under illumination at 360, 620, and 960 nm, implying the ability of broadband light detection in the UV, visible (VIS), and near infrared (NIR) region. Furthermore, a solar‐blind UV detection is demonstrated by integrating a solar‐blind UV filter with PQDCF coated EMCCD. In all, the use of PQDCF as luminescent downshifting materials provides an effective and low‐cost way to improve the UV response of Si photodetectors.