Small Molecule Approach to Passivate Undercoordinated Ions in Perovskite Light Emitting Diodes: Progress and Challenges

Nowadays, gas sensors with high response and short response/recovery time at room temperature (RT) are of great interest to researchers. This work demonstrated a gas sensor based on the composites of CsPbBr3 quantum dots (QDs) and ZnO microballs (MBs) for NO2 detection at room temperature. Compared with pure ZnO MBs, the composites decorated with 1.0 wt% QDs showed the optimal sensitivity under the 520 nm light activation. The response of 1.0 wt% QDs-ZnO sensor to 5 ppm NO2 was about 53, and the response/recovery time were about 63 s and 40 s, respectively. The sensor also showed good repeatability during four cycles and superior selectivity than other gases such as CO, NH3, and acetone. The addition of QDs can realize the absorption of visible light by the sensor and improve the utilization of light energy. Under the light excitation, the conductivity of the composites is significantly increased and the activity of oxygen species on the surface is also improved, which is conducive to the adsorption/desorption of gas molecules. 

CsPbBr3 quantum dots enhanced ZnO sensing to NO2 at room temperature

Solution-processed colloidal lead halide perovskite quantum dots (QDs) are considered one of the promising candidates for next-generation photovoltaics (PVs) due to the excellent optoelectronic properties and low-cost synthetic process. In particular, all-inorganic perovskite (AIP) QDs exhibit better prospects due to their better stability. Although remarkable breakthroughs have been made in bulk perovskite solar cells (SCs), the AIP QD-based SCs (AIPQDSCs) are still on their way to catch up. A lot of reports have summarized the development of perovskite SCs, but few have focused on AIPQDSCs. In this review, we focus on the latest development of AIPQDSCs, and analyze the current bottlenecks they are facing. Also, various optimization means have been discussed to improve the performance of AIPQDSCs from two perspectives of QD materials and device structure, including compositional regulation, surface engineering, interface engineering, and optimization of the carrier transport layer. In addition, AIP QDs as converter for SCs are also presented. Since the stability of perovskite SCs is currently the most pressing issue, the device stability is also highlighted. In the end, a brief summary and perspectives are presented to look forward to the future development of AIPQDSCs.

/pdf/all-inorganic-perovskite-quantum-dots-as-light-harvesting-4cz93p5pnn.pdf

All-inorganic perovskite quantum dots as light-harvesting, interfacial, and light-converting layers toward solar cells

Defect engineering to tune the light emission properties has been fetching lot of interest among scientific community for designing efficient optoelectronics and light-emitting diodes. Defect evolution in the trivalent ion-doped CeO2 and their dependence on the ionic radii of the trivalent dopant were probed using Rietveld refined powder X-ray diffraction, positron annihilation lifetime and photoluminescence spectroscopy. The photoluminescence of Eu3+, a known structural probe, is monitored with codoping of two other trivalent ions Y3+ and La3+ whose ionic radii are on either side of Eu3+. The studies showed that smaller dopants like Y3+ create oxygen vacancies that are closely associated with Y3+ and codoping does not cause significant enhancement in asymmetry in the emission from Eu3+. At the same time, vacancies created by La3+ are not strongly associated with La3+, and due to their stronger association with Eu3+, the asymmetry in the emission is enhanced. The study shows the usefulness of emission from Eu3+ as probe in understanding the effect of different trivalent dopants using them as codopants to Eu3+. The studies are expected to help in tuning the oxygen vacancy concentration as well as their migration in CeO2 for technological applications such as catalysis, magnetism and conductors. 
This work highlighted role of defect engineering in tailoring the optical properties of red emitting CeO2:Eu3+ phosphor via aliovalent and contrasting Y3+ and La3+ co-dopant.

Europium luminescence as a structural probe to understand defect evolution in CeO2/Eu3+, M3+ (M = Y and La): contrasting role of codopant ionic size

Lead halide-based perovskite quantum dots (PQDs) have recently emerged as an important class of nanocrystal (NC) materials for optoelectronic and photoelectrochemical applications. Thanks to their intriguing features including tunable band gap, narrow emission, high charge carrier mobility, remarkable light-absorbing factors, and long charge diffusion length, there has been a surge in research on lead halide-based PQDs and their applications. In this review, we showcase the fundamentals of PQDs and two principal applications including PQD solar cells (PQDSCs) and photocatalytic conversion. First, a thorough discussion on PQDSCs, their structure, surface treatment, and interface engineering along with their recent progress are presented. It is highlighted that the improvement of the efficiency of PQDSCs from below 10% to beyond 16% in a matter of a few years has turned them into promising candidates for future SC applications. Subsequently, the application of PQDs in photocatalytic reactions such as hydrogen production, CO2 reduction, and organic compounds’ degradation is summarized. Not to mention that, despite the remarkable properties of PQDs in SCs and photocatalysis, the inferior stability of PV devices based thereon under operation as well as their poor tolerance under air, water, light, and heat impede their widespread application. For this, the practical efforts and possible solutions are extensively addressed. Finally, an outlook is provided, addressing further merits, and demerits of each application as well as prospective opportunities. 

https://pubs.acs.org/doi/pdf/10.1021/acsanm.2c02787

Lead Halide Perovskite Quantum Dots for Photovoltaics and Photocatalysis: A Review

Recent progress on defect modulation for highly efficient metal halide perovskite light-emitting diodes

Innate immune cell instruction using micron-scale 3D objects of varied architecture and polymer chemistry: The ChemoArchiChip

Halide perovskite light-emitting diodes (PeLEDs) have attracted great attention because of their superior optical properties, such as extremely high photoluminescence (quantum yield up to nearly 100%) of active layers with tunable wavelengths over the entire visible spectral range. With a suitable modification of halide perovskites, carrier transport materials, and their interfaces, external quantum efficiencies exceeding 10%, 25%, and 20% have been achieved for blue-colored (465 nm), green-colored (512 nm), and red-colored (640 nm) LEDs, respectively. Many strategies for pursuing high performances of devices have been successfully demonstrated, among which ligand engineering has always played an important role in the active layer. Herein, we present a perspective to illustrate the effects and roles of the ligands in cesium lead bromide light-emitting diodes. This perspective is mainly classified into three parts: (1) ligands for CsPbBr3 LEDs could improve radiative recombination of perovskites and contribute to better efficiency of LEDs; (2) ligands could confine CsPbBr3 growth for blue emission of LEDs; (3) stabilities of materials and devices become better with ligand engineering. Finally, the summary and perspective on PeLEDs are highlighted and possible solutions are provided.

/pdf/toward-high-performances-of-halide-light-emitting-diodes-the-dcxiwdqp.pdf

Le Ma

Papers

All-inorganic perovskite quantum dots as light-harvesting, interfacial, and light-converting layers toward solar cells

Recent progress on defect modulation for highly efficient metal halide perovskite light-emitting diodes

Innate immune cell instruction using micron-scale 3D objects of varied architecture and polymer chemistry: The ChemoArchiChip

Toward High-Performances of Halide Light-Emitting Diodes: The Importance of Ligands Engineering