4 research outputs found

    Improved Electrical Transport and Electroluminescence Properties of p‑ZnO/n-Si Heterojunction via Introduction of Patterned SiO<sub>2</sub> Intermediate Layer

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    The authors report on the fabrication and temperature-dependent current–voltage and electroluminescence properties of p-ZnO:As/n-Si heterojunction diodes. The As-doped p-ZnO material was prepared by out-diffusion of arsenic atoms from a sandwiched GaAs interlayer on patterned SiO<sub>2</sub>/Si substrates. The introduction of hollow-shaped SiO<sub>2</sub> patterned layer promotes the efficiency of carrier injection into the active layer and considerably lowers the emission onset of the studied diode. The current–voltage characteristics of the heterojunction were detailedly studied in the temperature range of 21–120 °C to determine the dominant carrier transport mechanisms in different bias regions. The reverse saturation current, barrier height, and ideality factor were estimated from the thermionic emission model and found to be highly temperature dependent. An improved electroluminescence performance of the studied diode featuring an ultralow emission onset and an acceptable operation stability shows the potential of our approach. Long-term stability of the diode without encapsulation in air-exposure environment was also investigated by monitoring the electroluminescence evolution with storage time, and the oxygen-related surface adsorption was identified as the main cause for the undesirable emission decay

    High-Efficiency and Air-Stable Perovskite Quantum Dots Light-Emitting Diodes with an All-Inorganic Heterostructure

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    Perovskite light-emitting diodes (PeLEDs), because of its fundamental scientific importance and practical applications in the fields of low-cost light source or display applications, have drawn worldwide attention in recent years. However, PeLEDs available today suffer from a compromise in their emission efficiency and operation stability. In this study, we designed and fabricated a stacking all-inorganic multilayer structure by using inorganic perovskite CsPbBr<sub>3</sub> quantum dots (QDs) as the emissive layer and inorganic n-type MgZnO and p-type MgNiO as the carrier injectors, respectively. Through energy band engineering of carrier injectors by Mg incorporation and their thickness optimization, PeLEDs with maximum luminance of 3809 cd/m<sup>2</sup>, luminous efficiency of 2.25 cd/A, and external quantum efficiency of 2.39% have been realized, which are much better than most PeLEDs from CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> films, and comparable with the highest results reported on CsPbBr<sub>3</sub> QDs LEDs. More importantly, the unencapsulated PeLEDs in a continuous current mode demonstrate a remarkable operation stability against water and oxygen degradation. After a continuous operation for 10 h under a dc bias (10.0 V), nearly 80% of the original efficiency of the PeLEDs has been retained, greatly superior to reference and other previously reported devices constructed with conventional organic carrier injectors. Our results obtained open possibilities for the design and development of high-efficiency and air-stable PeLEDs that are not dependent on expensive and less-stable organic carrier injectors

    Photofacilitated Controllable Growth of ZnO Films Using Photoassisted Metal Organic Chemical Vapor Deposition

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    High-quality ZnO thin films were deposited on sapphire substrates using a photoassisted metal–organic chemical vapor deposition (PA-MOCVD) system. A controllable morphology evolution with varying degrees of crystallinity was observed. The microstructure of the film changes from a three-dimensional nanorod form to two-dimensional continuous dense form as the light irradiation intensity increases. A possible photofacilitated nucleation mechanism with a higher nucleation rate and density was proposed to explain the variation of the resulting ZnO formation. In this case, the crystallinity and optical properties of the epitaxial ZnO were also optimized, such that a low full width at half-maximum (0.079°) of the rocking curve could be obtained, similar to that of single-crystal ZnO. It was also found that the tensile strain in the films could be availably relaxed by added thermal energy and energetic photons provided by light irradiation. Additionally, temperature-dependent photoluminescence results behaving as strong exciton effects confirmed the relatively excellent quality of the obtained ZnO films

    Strategy of Solution-Processed All-Inorganic Heterostructure for Humidity/Temperature-Stable Perovskite Quantum Dot Light-Emitting Diodes

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    Recently, a pressing requirement of solid-state lighting sources with high performance and low cost has motivated increasing research in metal halide perovskites. However, the relatively low emission efficiency and poor operation stability of perovskite light-emitting diodes (LEDs) are still critical drawbacks. In this study, a strategy of solution-processed all-inorganic heterostructure was proposed to overcome the emission efficiency and operation stability issues facing the challenges of perovskite LEDs. Solution-processed n-ZnO nanoparticles and p-NiO are used as the carrier injectors to fabricate all-inorganic heterostructured CsPbBr<sub>3</sub> quantum dot LEDs, and a high-efficiency green emission is achieved with maximum luminance of 6093.2 cd/m<sup>2</sup>, external quantum efficiency of 3.79%, and current efficiency of 7.96 cd/A. More importantly, the studied perovskite LEDs possess a good operation stability after a long test time in air ambient. Typically, the devices can endure a high humidity (75%, 12 h) and a high working temperature (393 K, three heating/cooling cycles) even without encapsulation, and the operation stability is better than any previous reports. It is anticipated that this work will provide an effective strategy for the fabrication of high-performance perovskite LEDs with good stability under ambient and harsh conditions, making practical applications of such LEDs a real possibility
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