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

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

Among perovskites, the research on cesium lead iodides (CsPbI3) has attracted a large research community, owing to their all-inorganic nature and promising solar cell performance. Typically, the CsPbI3 solar cell devices are prepared at various heterojunctions, and working at fluctuating temperatures raises questions on the material stability-related performance of such devices. The fundamental studies reveal that their poor stability is due to a lower side deviation from Goldschmidt’s tolerance factor, causing weak chemical interactions within the crystal lattice. In the case of organic–inorganic hybrid perovskites, where their stability is related to the inherent chemical nature of the organic cations, which cannot be manipulated to improve the stability drastically whereas the stability of CsPbI3 is related to surface and lattice engineering. Thus, the challenges posed by CsPbI3 could be overcome by engineering the surface and inside the CsPbI3 crystal lattice. A few solutions have been proposed, including controlled crystal sizes, surface modifications, and lattice engineering. Various research groups have been working on these aspects and had accumulated a rich understanding of these materials. In this review, at first, we survey the fundamental aspects of CsPbI3 polymorphs structure, highlighting the superiority of CsPbI3 over other halide systems, stability, the factors (temperature, polarity, and size influence) leading to their phase transformations, and electronic band structure along with the important property of the defect tolerance nature. Fortunately, the factors stabilizing the most effective phases are achieved through a size reduction and the efficient surface passivation on the delicate CsPbI3 nanocrystal surfaces. In the following section, we have provided the up-to-date surface passivating methods to suppress the non-radiative process for near-unity photoluminescence quantum yield, while maintaining their optically active phases, especially through molecular links (ligands, polymers, zwitterions, polymers) and inorganic halides. We have also provided recent advances to the efficient synthetic protocols for optically active CsPbI3 NC phases to use readily for solar cell applications. The nanocrystal purification techniques are challenging and had a significant effect on the device performances. In part, we summarized the CsPbI3-related solar cell device performances with respect to the device fabrication methods. At the end, we provide a brief outlook on the view of surface and lattice engineering in CsPbI3 NCs for advancing the enhanced stability which is crucial for superior optical and light applications.

/pdf/cesium-lead-iodide-perovskites-optically-active-crystal-151be988.pdf

Cesium Lead Iodide Perovskites: Optically Active Crystal Phase Stability to Surface Engineering

Quantum dots (QDs) are facing significant photoluminescence degradation in moisture environment. In QDs-silicone composites, the poor water resistance of silicone matrix makes it easy for water and oxygen molecules to erode QDs. To tackle this issue, we proposed a new QDs protection strategy by introducing short-chain silica precursors onto the QDs’ surface, so that a dense silica passivation layer could be formed onto the QDs nanoparticles. Sol-gel method based on 3-aminopropyl triethoxysilane (APTES), 3-mercaptopropyl trimethoxysilane (MPTMS), and 3-mercaptopropyl triethoxysilane (MPTES) were adopted to prepare the uniform and crack-free QDs-silica glass (QD-glass). Because of the crosslinking of short-chain precursors, the formed silica glass possesses 38.6% smaller pore width and 68.6% lower pore volume than silicone, indicating its denser cross-linked network surrounding QDs. After 360 h water immersion, the QDs-glass demonstrated a 6% enhancement in red-light peak intensity, and maintained a stable full width at half maximum (FWHM) and peak wavelength, proving its excellent water-resistant ability. However, the conventional QDs-silicone composites not only showed a decrease of 75.3% in red-light peak intensity, but also a broadened FWHM and a redshifted peak wavelength after water immersion. QDs-glass also showed superior photostability after 132 h exposure to blue light. Red-light peak intensity of QDs-glass remained 87.3% of the initial while that of QDs-silicone decreased to 19.8%. And the intensity of QDs-glass dropped to 62.3% of that under 20 °C after thermal treatment of 160 °C. Besides, under increasing driving currents, the light conversion efficiency drop of QDs-glass is only one fifth that of QDs-silicone. Based on the QDs-glass, the white light-emitting diodes was achieved with a high luminous efficiency of 126.5 lm W−1 and a high color rendering index of 95.4. Thus, the newly proposed QD-glass has great significance in guaranteeing the working reliability of QDs-converted devices against moisture and high-power environment.

Enhancing oxygen/moisture resistance of quantum dots by short-chain, densely cross-linked silica glass network

All-inorganic CsPbX3 perovskite material not only has the benefits of advanced light absorption coefficient, long carrier lifetime, and simple preparation process of organic–inorganic perovskite materials but it also maintains excellent stability under the erosion of damp heat. Stability is the premise of its industrialization, so all-inorganic perovskite is undoubtedly a very competitive direction for the development of perovskite materials. However, there are still many defects in the all-inorganic perovskite thin films, and it is difficult to obtain high power conversion efficiency (PCE). This review systematically summarizes additive engineering, solvent engineering, and interface engineering methods to promote the thin film property for a high PCE in recent years.

/pdf/recent-progress-on-boosting-the-perovskite-film-quality-of-3go1zvhd.pdf

Recent Progress on Boosting the Perovskite Film Quality of All-Inorganic Perovskite Solar Cells

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

Fang Tao

Papers

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