Wavelength‐tunable nano/microlasers are essential components for various highly integrated and multifunctional photonic devices. Based on the different band gap/composition of inorganic cesium lead halide perovskite materials, broad band light absorption and emission devices can be achieved. Herein, a vapor–liquid–solid route for growing cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) microcrystal structures is demonstrated. These square‐shaped microstructures exhibit strong blue, green, and red photoluminescence, indicating that their band gaps can be engineered to cover the entire visible range. Optically pumped red–green–blue whispering‐gallery mode lasers based on the controlled composition of these microcrystals are successfully realized at room temperature. Moreover, rationally designed white‐light‐emitting chips with high brightness are fabricated utilizing these metal halide perovskite microstructures grown on sapphire. All these results evidently suggest a feasible route to the design of red–green–blue lasers and white‐light emitters for potential applications in full‐color displays as well as photonic devices.

The inorganic hole transport layer of nickel oxide (NiOx) has shown highly efficient, low‐cost, and scalable in perovskite photovoltaics. However, redox reactions at the interface between NiOx and perovskites limit their commercialization. In this study, ABABr (4‐(2‐Aminoethyl) benzoic acid bromide) between the NiOx and different perovskite layers to address the issues has been introduced. How the ABABr interacts with NiOx and perovskites is experimentally and theoretically investigated. These results show that the ABABr molecule chemically reacts with the NiOx via electrostatic attraction on one side, whereas on the other side, it forms a strong hydrogen bond via the NH3+ group with perovskites layers, thus directly diminishing the redox reaction between the NiOx and perovskites layers and passivating the layer surfaces. Additionally, the ABABr interface modification leads to significant improvements in perovskite film morphology, crystallization, and band alignment. The perovskites solar cells (PSCs) based on an ABABr interface modification show power conversion efficiency (PCE) improvement by over 13% and maintain over 90% of its PCE after continuous operation at maximum power point for over 500 h. The work not only contributes to the development of novel interlayers for stable PSCs but also to the understanding of how to prevent interface redox reactions.

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Oxide-based transparent p−n homojunctions are desirable for the development of transparent electronics. However, most oxide semiconductors are intrinsically n-type and to achieve p-type wide-gap oxide is still challenging. Previously, we have demonstrated that alloying a high-mobility n-type material such as CdO with p-type NiO can provide an avenue for electronic band engineering and consequently achieve bipolar conductivity in the midalloy composition. In this study, we synthesized O-rich Ni x Cd 1−x O alloys (Ni x Cd 1−x O 1+δ ) over the entire composition with Li and Cu doping using radio frequency (RF) magnetron sputtering at room temperature. We show that by Li and Cu doping the conductivity in the p-type regime of these alloys is improved, which also leads to a wider composition window for bipolar doping in Ni x Cd 1−x O. Specifically, by Li doping, the p-type alloy composition can be extended to x ≥ 0.3 so that the bipolar doping window is expanded to 0.30 ≤ x ≤ 0.52. Detailed measurements on electrical, structural, optical, and electronic properties suggest that Li is an effective acceptor, offering a promising way to improve the p-type conduction in Ni-rich Ni x Cd 1−x O alloys as well as to regulate the bipolar conductivity in this alloy system. A p-Ni 0.7 Cd 0.3 O:Li/n-Ni 0.45 Cd 0.55 O quasi-homojunction was fabricated and a rectification ratio ∼10 2 with an ideality factor of ∼2.9 was obtained. The demonstrated quasi-homojunction structure also showed >60% transmittance in the visible spectrum.

High mobility amorphous ionic oxide semiconductors (AIOSs) are ternary or quaternary heavy metal oxides which have been identified as technologically important materials for flexible transparent electronics because of their large area uniformity and low temperature processing compatibility. Here, we report on the room temperature synthesis of CdO-In2O3 alloy thin films in the full composition range using the magnetron sputtering technique on glass and plastic substrates. We found that alloys with a cation composition range of 10–55% Cd are amorphous with high mobility in the range of 30–45 cm2/Vs and an electron concentration of ∼3–4 × 1020 cm−3. The intrinsic and optical gap of these amorphous alloys varies from 2.7 to 3.2 eV and 3.2 to 3.4 eV, respectively. The room temperature processing, wide bandgap tunability, and low resistivity of ∼4–5 × 10−4 Ω cm make these amorphous films among the best AIOSs as transparent electrodes on flexible substrates.