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Artificial intelligence offers new opportunities for translucent displays. However, achieving translucent light-emitting diodes (LEDs) with high efficiency and high color purity remains a challenge. Here, we propose a strategy of using an alkali metal/inert metal (calcium/silver) bilayer metal electrode as a top electrode and perovskite nanocrystals as an emitter layer in the device structure, which allows us to not only fabricate excellent opaque LEDs but also manufacture highly efficient semitransparent LEDs with high color purity, total brightness (over 7000 cd m–2), total external quantum efficiency (over 12%), and 56% transmittance around 520 nm. This is the highest external quantum efficiency report about semitransparent LED based on perovskite materials or inorganic quantum dots so far, which presents great application potential in the field of translucent display with high color purity and wide color gamut.

For next-generation high-definition displays, the newly recommendation 2020 (Rec. 2020) standard calls for the emission wavelength of green emitters to be kept at 525–535 nm with narrow emission line width below 25 nm. All-inorganic lead halide perovskite CsPbBr3nanocrystals (NCs) with sharp emission seem as the prefect one to match the call, however, it is a great challenge to tune their emission wavelength to the target window of 525–535 nm because of the intrinsic band gap of CsPbBr3. Herein, we report a facile strategy to prepare CsPbBr3NCs with finely tunable emissions in the narrow range of 525–535 nm by establishing a CsPbBr3–Cs4PbBr6:Na Type II structure. The doping of the Na ions is the key factor to construct the Type II structure, which induces the formation of the Cs4PbBr6:Na phase and builds CsPbBr3–Cs4PbBr6:Na Type II structure, leading to the tunable emission wavelength of CsPbBr3NCs. The as-synthesized CsPbBr3NCs exhibit an ideal emission at 525–535 nm with a narrow emission line width of 23 nm and a high photoluminescence quantum yield (PLQY) of 85%. As a green downconverter, an ultrapure green backlight covers 97% of the Rec. 2020 standard in the CIE 1931 color space, representing the “greenest” backlight up to now.

Photoreduction of carbon dioxide (CO2) into fuels presents a promising approach to mitigate global warming and energy crises. Halide perovskite nanocrystals (NCs) with prominent optoelectronic properties have triggered substantial attention as photocatalysts but are limited by the charge recombination and instability. Here, we develop stable CsPbBr3/titania microspheres (TMs) by in situ growth of CsPbBr3NCs inside mesoporous TMs through solid-state sintering, which significantly improves the stability of perovskite NCs, making them applicable in water with efficient CO2photoreduction performance. Notably, the CsPbBr3/TMs demonstrates a 6.73- and 9.23-fold increase in the rate of CH4production compared to TMs and CsPbBr3, respectively. The internal electric field facilitates S-scheme charge transfer, enhancing the separation of electron–hole pairs, as evidenced by X-ray photoelectron spectroscopy and electron paramagnetic resonance analysis, which is pivotal for the selective photoreduction of CO2. These insights pave the way for the design of CsPbBr3-based photocatalysts with superior efficiency and stability.