LiJiong

Industrial emissions play a major role in the global methane budget. The Permian basin is thought to be responsible for almost half of the methane emissions from all U.S. oil- and gas-producing regions, but little is known about individual contributors, a prerequisite for mitigation. We use a new class of satellite measurements acquired during several days in 2019 and 2020 to perform the first regional-scale and high-resolution survey of methane sources in the Permian. We find an unexpectedly large number of extreme point sources (37 plumes with emission rates >500 kg hour^–1), which account for a range between 31 and 53% of the estimated emissions in the sampled area. Our analysis reveals that new facilities are major emitters in the area, often due to inefficient flaring operations (20% of detections). These results put current practices into question and are relevant to guide emission reduction efforts.

In situ surface fluorination of TiO₂ nanocrystals affords record efficiency of planar perovskite solar cells: Low-temperature solution-processed fluorinated TiO₂ nanocrystals are applied as a novel electron transport layer of regular-structure planar heterojunction perovskite solar cells, affording the best power conversion efficiency (PCE) of 22.68%. F-doping improves the stabilities of devices, especially UV-light stability due to inhibited photocatalytic activity of TiO₂.

Abstract

Low-temperature solution-processed TiO₂ nanocrystals (LT-TiO₂) have been extensively applied as electron transport layer (ETL) of perovskite solar cells (PSCs). However, the low electron mobility, high density of electronic trap states, and considerable photocatalytic activity of TiO₂ result in undesirable charge recombination at the ETL/perovskite interface and notorious instability of PSCs under ultraviolet (UV) light. Herein, LT-TiO₂ nanocrystals are in situ fluorinated via a simple nonhydrolytic method, affording formation of Ti─F bonds, and consequently increase electron mobility, decrease density of electronic trap states, and inhibit photocatalytic activity. Upon applying fluorinated TiO₂ nanocrystals (F-TiO₂) as ETL, regular-structure planar heterojunction PSC (PHJ-PSC) achieves a champion power conversion efficiency (PCE) of 22.68%, which is among the highest PCEs for PHJ-PSCs based on LT-TiO₂ ETLs. Flexible PHJ-PSC devices based on F-TiO₂ ETL exhibit the best PCE of 18.26%, which is the highest value for TiO₂-based flexible devices. The bonded F atoms on the surface of TiO₂ promote the formation of Pb─F bonds and hydrogen bonds between F⁻ and FA/MA organic cations, reinforcing interface binding of perovskite layer with TiO₂ ETL. This contributes to effective passivation of the surface trap states of perovskite film, resulting in enhancements of device efficiency and stability especially under UV light.

Liquid-exfoliated 2D transition-metal dichalcogenides (MoS₂, WS₂, and WSe₂) are introduced as growth templates for spin-coated FASnI₃ perovskite films, leading to van der Waals epitaxial growth of perovskite grains with a growth orientation along (100). The good energy alignment in the NiO _x /WSe₂/FASnI₃ structure facilitates hole extraction and suppresses interfacial charge recombination, leading to the best PCE of 10.47% for the PSC.

Abstract

Tin (Sn)-based perovskites with favorable optoelectronic properties and ideal bandgaps have emerged as promising alternatives to toxic lead (Pb)-based perovskites for photovoltaic applications. However, it is challenging to obtain high-quality Sn-based perovskite films by solution process. Here, liquid-exfoliated 2D transition-metal dichalcogenides (i.e., MoS₂, WS₂, and WSe₂) with smooth and defect-free surfaces are applied as growth templates for spin-coated FASnI₃ perovskite films, leading to van der Waals epitaxial growth of perovskite grains with a growth orientation along (100). The authors find that WSe₂ has better energy alignment with FASnI₃ than MoS₂ and WS₂ and results in a cascade band structure in resultant perovskite solar cells (PSCs), which can facilitate hole extraction and suppress interfacial charge recombination in the devices. The WSe₂-modified PSCs show a power conversion efficiency up to 10.47%, which is among the highest efficiency of FASnI₃-based PSCs. The appealing solution phase epitaxial growth of FASnI₃ perovskite on 2D WSe₂ flakes is expected to find broad applications in optoelectronic devices.

Due to their suitable electrical and optical properties, ZnO nanostructure-based organic light-emitting diodes (LEDs) and perovskite LEDs can be utilized in the optoelectronics industry. A combination of ZnO nanorods and nanotubes with various types of polymers or hybrid perovskites leads to better waveguides and transportation of carriers. Therefore, more efficient LEDs are offered to the industry. In this research, four devices, including ZnO nanorod (nanotube)/MEH-PPV (CH 3 NH 3 PbI 3 ) LEDs are simulated by SILVACO TCAD software. To provide deeper understanding of the impact of applying nanorods and nanotubes in hybrid heterostructures, an ab initio study has been conducted and the electronic structure, density of states, absorption coefficient and dielectric function of each of these nanostructures have been scrutinized. Subsequently, the obtained data have been utilized in the SILVACO simulation, and characteristics such as the current–vol...

Perovskite light‐emitting diodes attract much attention because of their advantages such as high color purity, easy and wide color tunability, and high photoluminescence quantum yields. The recent developments of ideal multifunctional charge transport layers are discussed by considering the fundamental limitations including defects, morphological and phase instability, high refractive index, and poor outcoupling of perovskites.

Abstract

Despite their low exciton‐binding energies, metal halide perovskites are extensively studied as light‐emitting materials owing to narrow emission with high color purity, easy/wide color tunability, and high photoluminescence quantum yields. To improve the efficiency of perovskite light‐emitting diodes (PeLEDs), much effort has been devoted to controlling the emitting layer morphologies to induce charge confinement and decrease the nonradiative recombination. The interfaces between the emitting layer and charge transporting layer (CTL) are vulnerable to various defects that deteriorate the efficiency and stability of the PeLEDs. Therefore, the establishment of multifunctional CTLs that can improve not only charge transport but also critical factors that influence device performance, such as defect passivation, morphology/phase control, ion migration suppression, and light outcoupling efficiency, are highly required. Herein, the fundamental limitations of perovskites as emitters (i.e., defects, morphological and phase instability, high refractive index with poor outcoupling) and the recent developments with regard to multifunctional CTLs to compensate such limitations are summarized, and their device applications are also reviewed. Finally, based on the importance of multifunctional CTLs, the outlook and research prospects of multifunctional CTLs for the further improvement of PeLEDs are discussed.

This work reports a compatible strategy to enhance the efficiency of planar n–i–p Sb₂Se₃ solar cells through Sb₂Se₃ surface modification and an architecture with oriented 1D van der Waals material, trigonal selenium (t‐Se). The p‐type t‐Se layer functionally works as a surface passivation and hole transport material. The all‐inorganic device structure enables high efficiency and superb stability.

Abstract

Environmentally benign and potentially cost‐effective Sb₂Se₃ solar cells have drawn much attention by continuously achieving new efficiency records. This article reports a compatible strategy to enhance the efficiency of planar n–i–p Sb₂Se₃ solar cells through Sb₂Se₃ surface modification and an architecture with oriented 1D van der Waals material, trigonal selenium (t‐Se). A seed layer assisted successive close spaced sublimation (CSS) is developed to fabricate highly crystalline Sb₂Se₃ absorbers. It is found that the Sb₂Se₃ absorber exhibits a Se‐deficient surface and negative surface band bending. Reactive Se is innovatively introduced to compensate the surface Se deficiency and form an (101) oriented 1D t‐Se interlayer. The p‐type t‐Se layer promotes a favored band alignment and band bending at the Sb₂Se₃/t‐Se interface, and functionally works as a surface passivation and hole transport material, which significantly suppresses interface recombination and enhances carrier extraction efficiency. An efficiency of 7.45% is obtained in a planar Sb₂Se₃ solar cell in superstrate n–i–p configuration, which is the highest efficiency for planar Sb₂Se₃ solar cells prepared by CSS. The all‐inorganic Sb₂Se₃ solar cell with t‐Se shows superb stability, retaining ≈98% of the initial efficiency after 40 days storage in open air without encapsulation.

A composite consisting of 1D cation‐doped TiO₂ brookite nanorod embedded by 0D fullerene is investigated as a top modification buffer for inverted perovskite photovoltaic (IP‐PV) cells. The resultant IP‐PV displays an efficiency exceeding 22% with a favorable stability. This work opens up more opportunities in expanding the material inventory for charge transfer layer in perovskite solar cells development and application.

Abstract

Simultaneously achieving high efficiency and high durability in perovskite solar cells is a critical step toward the commercialization of this technology. Inverted perovskite photovoltaic (IP‐PV) cells incorporating robust and low levelized‐cost‐of‐energy (LCOE) buffer layers are supposed to be a promising solution to this target. However, insufficient inventory of materials for back‐electrode buffers substantially limits the development of IP‐PV. Herein, a composite consisting of 1D cation‐doped TiO₂ brookite nanorod (NR) embedded by 0D fullerene is investigated as a top modification buffer for IP‐PV. The cathode buffer is constructed by introducing fullerene to fill the interstitial space of the TiO₂ NR matrix. Meanwhile, cations of transition metal Co or Fe are doped into the TiO₂ NR to further tune the electronic property. Such a top buffer exhibits multifold advantages, including improved film uniformity, enhanced electron extraction and transfer ability, better energy level matching with perovskite, and stronger moisture resistance. Correspondingly, the resultant IP‐PV displays an efficiency exceeding 22% with a 22‐fold prolonged working lifetime. The strategy not only provides an essential addition to the material inventory for top electron buffers by introducing the 0D:1D composite concept, but also opens a new avenue to optimize perovskite PVs with desirable properties.

Semiconductor microcavities can greatly enhance the light-emission of embedded quantum dots (QDs). Here, a new route toward the microcavity-QD system by fabricating microcavities followed by growing ordered QDs on a patterned microresonator is proposed, which keeps QDs from being etched. Self-assembled Ge QDs prefer to form at the rims of Si microrings or microdisks. The Ge QDs on the pit- or groove-patterned microring resonator (MRR) show better size uniformity and position accuracy. These features are explained by the evolutions of surface morphology and surface chemical potential distribution. Sharp photoluminescence peaks in the telecommunication band with the quality factors in the range of 450–850 from groove-patterned MRR are observed at 295 K due to efficient overlap between Ge QDs and resonant modes. Our schemes shed light on the exactly site-controlled growth of QDs on micro- and nano-structures, which further facilitates the investigation of light-matter interactions....