All-inorganic Perovskite Quantum Dots Research Articles

Flexible and Self-Powered Photodetector Arrays Based on All-Inorganic CsPbBr3 Quantum Dots.

Flexible devices are garnering substantial interest owing to their potential for wearable and portable applications. Here, flexible and self-powered photodetector arrays based on all-inorganic perovskite quantum dots (QDs) are reported. CsBr/KBr-mediated CsPbBr3 QDs possess improved surface morphology and crystallinity with reduced defect densities, in comparison with the pristine ones. Systematic material characterizations reveal enhanced carrier transport, photoluminescence efficiency, and carrier lifetime of the CsBr/KBr-mediated CsPbBr3 QDs. Flexible photodetector arrays fabricated with an optimum CsBr/KBr treatment demonstrate a high open-circuit voltage of 1.3 V, responsivity of 10.1 A W-1 , specific detectivity of 9.35 × 1013 Jones, and on/off ratio up to ≈104 . Particularly, such performance is achieved under the self-powered operation mode. Furthermore, outstanding flexibility and electrical stability with negligible degradation after 1600 bending cycles (up to 60°) are demonstrated. More importantly, the flexible detector arrays exhibit uniform photoresponse distribution, which is of much significance for practical imaging systems, and thus promotes the practical deployment of perovskite products.

CsPbBr3–Ti3C2Tx MXene QD/QD Heterojunction: Photoluminescence Quenching, Charge Transfer, and Cd Ion Sensing Application

A Van der Waal heterostructure between the all-inorganic CsPbBr3 halide perovskite quantum dots (CPB QDs) and Ti3C2Tx MXene (MXN) QDs is realized and the photo-physics of the composite is examined....

Diammonium Porphyrin-Induced CsPbBr3 Nanocrystals to Stabilize Perovskite Films for Efficient and Stable Solar Cells.

Employing all-inorganic perovskite quantum dots (QDs) to treat organic-inorganic perovskite films has been well documented as a serviceable tactic to improve the performance of perovskite solar cells (PSCs). However, the inert molecule-coated QDs with zero-dimensional (0D) structure would limit further enhancement of the efficiency and stability of PSCs. Here, we employ a conductive diammonium porphyrin (ZnPy-NH3Br) to treat CsPbBr3 QDs coated on a three-dimensional perovskite film, thus constructing a stable 0D-two-dimensional perovskite capping layer. The generation of large-scale nanocube crystals by treating CsPbBr3 nanocrystallites with ZnPy-NH3Br in solution demonstrates such an assembly strategy. The formed capping layer can achieve efficient charge transport and separation. As a consequence, the best efficiency of an optimized device is up to 20.0%, which is superior to the control PSCs fabricated without modification (19.1%) and with pure CsPbBr3 QD modification (19.5%). More importantly, the porphyrin-treated CsPbBr3 QD-based devices retain over 65 or 85% of their initial efficiency when placed at 85 °C or 45% humidity tracking for 1000 h, respectively. Also, with the incorporation of QD-Por, the device retained 85% of the original efficiency when illuminated at AM 1.5 G for 450 h. Therefore, this work offered a facile avenue to modify perovskite films for fabricating highly efficient and stable PSCs.

High Efficiency Mesoscopic Solar Cells Using CsPbI3 Perovskite Quantum Dots Enabled by Chemical Interface Engineering.

All-inorganic α-CsPbI3 perovskite quantum dots (QDs) are attracting great interest as solar cell absorbers due to their appealing light harvesting properties and enhanced stability due to the absence of volatile organic constituents. Moreover, ex situ synthesized QDs significantly reduce the variability of the perovskite layer deposition process. However, the incorporation of α-CsPbI3 QDs into mesoporous TiO2 (m-TiO2) is highly challenging, but these constitute the best performing electron transport materials in state-of-the-art perovskite solar cells. Herein, the m-TiO2 surface is engineered using an electron-rich cesium-ion containing methyl acetate solution. As one effect of this treatment, the solid-liquid interfacial tension at the TiO2 surface is reduced and the wettability is improved, facilitating the migration of the QDs into m-TiO2. As a second effect, Cs+ ions passivate the QD surface and promote the charge transfer at the m-TiO2/QD interface, leading to an enhancement of the electron injection rate by a factor of 3. In combination with an ethanol-environment smoothing route that significantly reduces the surface roughness of the m-TiO2/QD layer, optimized devices exhibit highly reproducible power conversion efficiencies exceeding 13%. The best cell with an efficiency of 14.32% (reverse scan) reaches a short-circuit current density of 17.77 mA cm-2, which is an outstanding value for QD-based perovskite solar cells.

全无机钙钛矿量子点的合成、性质及发光二极管应用进展

全无机钙钛矿量子点的合成、性质及发光二极管应用进展

Synaptic Transistor Capable of Accelerated Learning Induced by Temperature-Facilitated Modulation of Synaptic Plasticity.

Neuromorphic computation, which emulates the signal process of the human brain, is considered to be a feasible way for future computation. Realization of dynamic modulation of synaptic plasticity and accelerated learning, which could improve the processing capacity and learning ability of artificial synaptic devices, is considered to further improve energy efficiency of neuromorphic computation. Nevertheless, realization of dynamic regulation of synaptic weight without an external regular terminal and the method that could endow artificial synaptic devices with the ability to modulate learning speed have rarely been reported. Furthermore, finding suitable materials to fully mimic the response of photoelectric stimulation is still challenging for photoelectric synapses. Here, a floating gate synaptic transistor based on an L-type ligand-modified all-inorganic CsPbBr3 perovskite quantum dots is demonstrated. This work provides first clear experimental evidence that the synaptic plasticity can be dynamically regulated by changing the waveforms of action potential and the environment temperature and both of these parameters originate from and are crucial in higher organisms. Moreover, benefiting from the excellent photoelectric properties and stability of quantum dots, a temperature-facilitated learning process is illustrated by the classical conditioning experiment with and without illumination, and the mechanism of synaptic plasticity is also demonstrated. This work offers a feasible way to realize dynamic modulation of synaptic weight and accelerating the learning process of artificial synapses, which showed great potential in the reduction of energy consumption and improvement of efficiency of future neuromorphic computing.

Reinforcing effects of waterproof substrate on the photo-, thermal and pH stabilities of perovskite nanocrystals

Lead halide perovskites have generated remarkable progress in a wide variety of opto-electronic fields. However, challenging issues including water-sensitive feature, poor stability over temperature change and mechanical fragility should be circumvented to enable the practical uses of such nanocrystals. Ethylene-propylene-diene monomer (EPDM) rubber, which possesses saturated and nonpolar polymeric chain, has been extensively explored in industry due to its sealing property, low-cost, dynamic and outstanding abrasive resistance. In this study, the hybrid inorganic-organic network with covalent cross-linkages and CsPbX3 (X = Cl and Br) quantum dots has been established in EPDM rubber system via an effective and mild approach in the process of mixing reaction at room temperature. In contrast to pure perovskite dots, the peak emission intensity of CsPb(Cl0·25Br0.75)3-EPDM can be well maintained after it has been immersed into aqueous solution for 2 h. Moreover, the water-mediated treatment will control the emission color evolution from cyan (485 nm) to green (510 nm) and such process can be fully reversible during the soaking and drying cycles. In addition, the employment of such polymeric host with superior heat resistance results in significant increases in thermal stability, mechanical strength and toughness. This efficient strategy will provide a rational design of reinforcing photoluminescence for all-inorganic perovskite quantum dots in numerous applications.

Stabilizing CsPbBr3 perovskite quantum dots on zirconium phosphate nanosheets through an ion exchange/surface adsorption strategy

All-inorganic perovskite quantum dots (PQDs) being characterized by high photoluminescence quantum yield, tunable emission colors and high color purity attract enormous attention in optoelectronic fields, especially as highly efficient narrow-band phosphors for lighting and next-generation display devices. However, poor stability seriously impedes their practical applications. Herein, we proposed an ion exchange/surface adsorption strategy to realize the room-temperature synthesis and stabilization of CsPbBr3 PQDs on α-Zr(HPO4)2·H2O (zirconium phosphate, α-ZrP) nanosheets. The inherent characteristics of the α-ZrP nanosheets including high Pb2+ adsorptivity and good Cs+ ion exchange capability promoted the heterogeneous nucleation-growth and effective anchoring of CsPbBr3 PQDs on α-ZrP surfaces. Consequently, the synthesized α-ZrP/CsPbBr3 composite exhibited superior green-emitting performance and significantly enhanced humidity stability and thermal stability in comparison to pure PQDs and many other matrix-protected PQDs. All these favorable characteristics listed above endowed the α-ZrP/CsPbBr3 composite with good optical properties for lighting and displays. This work opens up a new way to use inorganic nanomaterials to stabilize all-inorganic PQDs and can promote the scalable synthesis of PQDs with long-term stability for optoelectronic devices.

Ultrafast Charge Separation and Recombination across a Molecule/CsPbBr3 Quantum Dot Interface from First-Principles Nonadiabatic Molecular Dynamics Simulation

All-inorganic perovskite quantum dots (QDs) hold great promise in photovoltaic solar cells. However, the reduced dimensionality of QDs confines the photoexcited electron–hole pairs, suppresses charge separation, and accelerates charge recombination (CR), limiting the photon-to-electron conversion efficiency of a solar cell. Molecule passivation can overcome this shortcoming via efficiently extracting charge carriers from QDs. Using a combination of time-domain density functional theory and nonadiabatic (NA) molecular dynamics, we demonstrate that low-frequency vibrations promoted both charge separation and recombination. The photoexcited excitons on a CsPbBr3 QD can efficiently dissociate into free charge carriers via rapid interfacial electron transfer (ET) and hole transfer (HT) to a binding benzoquinone (BQ) and a phenothiazine (PTZ) molecule on similar sub-100 ps time scales, respectively. This is manifested by the fact that the QD-BQ system holds smaller energy gap and NA coupling between the donor a...

Ru‐Shi Liu

"The secret of being a successful scientist is to contribute results that benefit humanity. My biggest inspiration is to develop an idea which can come true …" Find out more about Ru-Shi Liu in his Author Profile.

Anion- and Cation-Codoped All-Inorganic Blue-Emitting Perovskite Quantum Dots for Light-Emitting Diodes

Despite the high green photoluminescent quantum yield (PLQY) of CsPbBr3 quantum dots (QDs), achieving high blue photoluminescence with fully inorganic perovskite QDs via a simple synthesis method i...

MOF-Confined Sub-2 nm Stable CsPbX3 Perovskite Quantum Dots.

The metal halide with a perovskite structure has attracted significant attention due to its defect-tolerant photophysics and optoelectronic features. In particular, the all-inorganic metal halide perovskite quantum dots have potential for development in future applications. Sub-2 nm CsPbX3 (X = Cl, Br, and I) perovskite quantum dots were successfully fabricated by a MOF-confined strategy with a facile and simple route. The highly uniform microporous structure of MOF effectively restricted the CsPbX3 quantum dots aggregation in a synthetic process and endowed the obtained sub-2 nm CsPbX3 quantum dots with well-dispersed and excellent stability in ambient air without a capping agent. The photoluminescence emission spectra and lifetimes were not decayed after 60 days. The CsPbX3 quantum dots maintained size distribution stability in the air without any treatment. Because of the quantum confinement effect of CsPbX3 quantum dots, the absorption and photoluminescence (PL) emission peak were blue shifted to shorter wavelengths compare with bulk materials. Furthermore, this synthetic strategy provides a novel method in fabricating ultra-small photoluminescence quantum dots.

Water-stable all-inorganic CsPb1-XSnXBr2I perovskite quantum dots encapsulated in paraffin for white light-emitting diodes

All-inorganic perovskite quantum dots (QDs) have become a hot material in the field of photoelectricity due to their excellent properties, such as high photoluminescence quantum yields (PLQYs), narrow emission wavelengths, and easily controlled PL spectra and particle sizes. However, colloidal perovskite QDs are readily oxidized, degraded in a humid environment, and generated by ion exchange. Here, the CsPb1-XSnXBr2I QDs were synthesized successfully, which the Sn2+ ions partly replacing Pb2+ to reduce the toxicity of Pb-based perovskite. The tunable PL spectrum and band gap from 2.27 to 2.14 eV were obtained by adjusting the Sn content. Meanwhile, we adopted a simple, green and low-cost approach to encapsulated CsPb1-XSnXBr2I QDs within solid paraffin, which not only greatly improved the water stability of QDs, but also maintained outstanding luminous intensity after being immersed in water for 20 days. Finally, the while light-emitting diodes (WLEDs) with varying correlated color temperature (CCT), color rendering index (CRI) and luminous efficiency (LE) based on a combination of blue chip, P–CsPb1-XSnXBr2I QDs and red phosphor were successfully achieved.

CsPbCl3 perovskite quantum dots/TiO2 inverse opal photonic crystals for efficient photoelectrochemical detection of alpha fetoprotein

All-inorganic perovskite quantum dots (PQDs) have caused extensive research interest because of their excellent optical and electrical properties. However, their water-instability limits their biological applications, and the researches of photoelectrochemical (PEC) biological detection based on CsPbCl3 PQDs are relatively rarely. In this report, the PEC biosensor based on CsPbCl3 QDs modified macroporous TiO2 inverse opal photonic crystals (IOPCs) is designed for alpha fetoprotein (AFP) detection. Firstly, the water stability of PQDs immobilized on IOPCs is remarkably enhanced. In addition, the large specific surface area of TiO2 IOPCs improves the fixed amount of AFP and decreases the electron transmission distance between PQDs and FTO substrate. Ultimately, the PEC biosensor based on TiO2 IOPCs/CsPbCl3 shows excellent detection performance with a low detection limit of 30 pg ml−1 and a good linear range from 0.08 ng ml−1 to 980 ng ml−1 for AFP detection in phosphate buffer saline solutions. This detection system has very extensive application prospect for AFP detection in clinical analysis and biological fields.

All-inorganic perovskite quantum dots CsPbX3 (Br/I) for highly sensitive and selective detection of explosive picric acid

As a new family of fluorescent materials, all inorganic perovskite quantum dots (PQDs) CsPbX3 (Cl, Br, I) have attracted rising attention due to their intrinsic optical superiorities and potential applications in various fields. This work takes advantage of the bright fluorescence of PQDs and the strong electrophilic properties of picric acid (PA) to construct an analytical method for sensitive and selective discrimination of PA against other nitroaromatic explosives, and the limit of detection is as low as 0.8 nM. The quenching mechanism was elucidated as the formation of electrostatic complex and the electron transfer between PA and PQDs. To facilitate visual and on-site detection, the CsPbBr3 PQDs were printed onto microfiltration membrane by inkjet printing to fabricate test papers for rapid and on-site detections of explosive and pollutant PA, showing a great research prospect in the detection of ultratrace PA at different sites.

Radiation-pressure-induced photoluminescence enhancement of all-inorganic perovskite CsPbBr3 quantum dots

Perovskite quantum dots (QDs) are of great interest due to their outstanding optoelectronic properties and tremendous application potential. Improving photoluminescence (PL) spectra in all-inorganic perovskite QDs is of great importance for performance enhancement. In this work, the PL quantum yield of the CsPbBr3 perovskite QDs is enhanced from 70% to 95% with increasing radiation pressure. Such enhancement is attributed to the increased binding energy of self-trapped excitons (STEs) upon radiation pressure, which is consistent with its blue-shifted PL and other characterization results. Furthermore, we study ultrafast absorption spectroscopy and find that the dynamics of relaxation from free excitons to STEs in radiation pressure CsPbBr3 QDs is ascribed to stronger electron–phonon coupling in the contracted octahedral structure. It is further demonstrated that radiation pressure can boost the PL efficiency and explore effectively the relationship between the structure and optical properties.

Constructing Gradient Energy Levels to Promote Exciton Energy Transfer for Photoluminescence Controllability of All-Inorganic Perovskites and Application in Single-Component WLEDs

Photoluminescence tunability is exceedingly crucial to all-inorganic halide perovskite (CsPbX3, X = Cl, Br, I) quantum dots (QDs) for high-resolution display. However, up to now, the wide-range col...

Light enhanced low-voltage nonvolatile memory based on all-inorganic perovskite quantum dots

Light enhanced low-voltage nonvolatile memory was prepared using all-inorganic perovskite quantum dots (QDs) as a semiconductor layer and Ag nanoparticles (NPs) as a floating gate layer. The photo-induced carriers can be produced in CsPbBr3 QDs under ultraviolet light and trapped in Ag NPs under the action of an external electric field. With the assistance of light, the device exhibited a significantly larger memory window (ΔVth) under low programming and erasing voltages of ±5 V owing to the use of CsPbBr3 QDs. Furthermore, we proved that the ΔVth of the memory strongly depended on the applied bias voltage (VDS) as well as still remaining at 79.3% after 105 s at VDS of 1.4 V. The facile memory provides a new approach to trap a photo-induced charge and reduce operating voltages by combining QDs with metal NPs.

Flexible, Printable Soft-X-Ray Detectors Based on All-Inorganic Perovskite Quantum Dots.

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.

Radioluminescent nuclear battery containing CsPbBr 3 quantum dots: Application of a novel wave‐shifting agent

Radioluminescent nuclear battery has been widely studied for its miniaturization and long life. In this study, all-inorganic perovskite quantum dots (CsPbBr3 QDs) were selected as a novel wave-shifting agent combined with liquid scintillator PPO (2,5-diphenyloxazole). The QDs were used to regulate the emission spectrum to match different GaAs devices. The maximum output power of the RL nuclear battery was greatly enhanced by 1.91 to 2.53 times. Perovskite QDs with adjustable emission spectra were used as wave-shifting agents and exhibited more excellent properties and application prospects than traditional wave-shifting agents. The Monte Carlo method was used to simulate the energy deposition of fluorescent materials under various radioactive source models. Results verified the advantages of using liquid radioactive sources and liquid fluorescent materials. The application and reference value of perovskite QDs in nuclear detection and nuclear medical imaging were also discussed.