Recent advancements have led to the development of bright and heavy metal-free blue-emitting quantum dot light-emitting diodes (QLEDs). However, consensus understanding of their distinct photophysical and electroluminescent dynamics remains elusive. This work correlates the chemical and electronic changes occurring in a QLED during operation using depth-resolved and operando techniques. The results indicate that oxygen vacancy forms in the ZnMgO layer during operation, with important implications on the charge injection and electrochemical dynamics. Taken together, the results suggest a causal relationship between oxygen vacancy formation and operational degradation of the blue-emitting ZnSeTe-based QLEDs.

Over the recent few years, extensive research efforts have shifted from normal (n-i-p) to inverted (p-i-n) perovskite solar cells (PSCs), owing to their promising efficiency and operational stability, enabled by low-temperature processing. Despite a fundamentally identical operation principle (only structurally inverted), the optimized perovskite compositions for normal and inverted PSCs differ significantly across the literature, suggesting an underlying design principle for perovskite composition. Here, we unveil the role of cesium cation in enhancing interfacial contact between the perovskite layer and the underlying hole-transporting layer (HTL) in inverted PSCs. Comprehensive in situ and device characterization reveal that cesium incorporation promotes the formation of initial nucleation seeds for heterogeneous nucleation at the perovskite/hydrophobic HTL interface, thereby improving their contact. The resulting compositional heterogeneity explains the focus of recent studies on resolving this issue. This study provides mechanistic insight into designing perovskite compositions to further enhance the performance and longevity of PSCs.

Syngas from gasification is converted into hydrogen and CO2 through the water-gas shift (WGS) reaction, and the subsequent pressure swing adsorption (PSA) separation produces high-purity hydrogen while capturing high-concentration of CO2. The collected CO2 can be utilized, at least as a feedstock for dry ice, which is in short supply in many countries. There are still many under-utilized low-grade feedstocks, such as pet-coke, biomass, and waste. These feedstocks can serve as good starting materials for producing economically feasible hydrogen for fuel cell power generation and hydrogen-fueled automobiles. Gasification technology is effective at breaking down low-grade feedstocks into syngas (CO + H2). However, in pet-coke gasification, there is an additional challenge due to its high sulfur content, which necessitates extensive desulfurization. Specifically, to use hydrogen in fuel cells, the residual sulfur concentration in hydrogen must be reduced to below 0.1 ppm. Over the last 3 years, a 2-ton/day pilot plant has been operated to produce high-purity hydrogen from pet-coke, using gasification, desulfurization, WGS, and PSA units. Based on the results from the pilot plant, a scaled-up 20-ton/day demonstration plant was constructed, yielding preliminary results toward the ultimate goal of producing blue hydrogen. Operation results show that sulfur containing impurities can be reduced to less than 0.1 ppm, and hydrogen of 99.9% purity can be obtained after WGS and PSA units. Several business models were proposed to utilize the developing process by module approach.

The two-dimensional on three-dimensional (2D/3D) perovskite bilayer heterostructure can improve the stability and performance of perovskite solar cells. We show that the 2D/3D perovskite stack in a device evolves dynamically during its end-of-life decomposition. Initially phase-pure 2D interlayers can evolve differently, resulting in different device stabilities. We show that a robust 2D interlayer can be formed using mixed solvents to regulate its crystallinity and phase purity. The resulting 2D/3D devices achieved 25.9% efficiency and had good durability, retaining 91% of their initial performance after 1074 hours at 85°C using maximum power point tracking.

Abstract State-of-the-art wide bandgap perovskite compositions for perovskite/silicon tandem solar cells often incorporate methylammonium (MA) containing multi-cation-mixed-halides compositions to achieve high efficiency. However, the MA-containing perovskite films and devices are likely to suffer from photo and thermal instability due to volatile MA + cations. Here, systematic investigation on MA-free FA 1– x Cs x PbI 3– y Br y perovskite compositions was conducted to devise an effective MA-free wide bandgap composition. The Cs + content was found to play a central role in optimizing the purity and stability of the desired perovskite phase. With varying Cs + contents, a trade-off between structural formability of the perovskite phase and lattice microstrain was observed. Balancing the sacrificial trade-off was found to be critical in minimizing the trap densities to achieve high performance and stable wide bandgap perovskite solar cells. Our findings provide insights into the development of an optimal perovskite composition for high efficiency and stable perovskite-based tandem solar cells.