Lead‐based organic–inorganic hybrid perovskite materials are widely used in optoelectronic devices due to their excellent photophysical properties. However, the main issues which hinder its commercialization are the toxicity caused by lead and the intrinsic instability of the material. Recently, many lead‐free halide materials with good intrinsic stability have been reported, among which bismuth‐based halide materials have attracted extensive research due to their structure and promising optoelectronic properties. In this review, bismuth‐based materials are divided into binary BiX3 (X = I, Br, Cl), ternary AaBibXa+3b (A = Cs, Rb, MA, Ag, etc.), and quaternary A2AgBiX6 (A = Cs, Rb, MA, etc.) according to its elemental composition. The structure and optoelectronic properties of bismuth‐based halide materials, which may be helpful for the development of bismuth‐based halide materials and lead‐free perovskites in the future, are summarized and highlighted.

All‐inorganic CsPbI2Br perovskite has attracted increasing attention, owing to its outstanding thermal stability and suitable bandgap for optoelectronic devices. However, the substandard power conversion efficiency (PCE) and large energy loss (Eloss) of CsPbI2Br perovskite solar cells (PSCs) caused by the low quality and high trap density of perovskite films still limit the application of devices. Herein, the post‐treatment of evaporating cesium bromide (CsBr) is utilized on top of the perovskite surface to passivate the CsPbI2Br–hole‐transporting layer interface and reduce Eloss. The results of microzone photoluminescence indicate that the evaporated CsBr gathered at the grain boundaries of CsPbI2Br layers and Br‐enriched perovskites (CsPbIxBr3−x, x < 2) are formed, which can provide protection for CsPbI2Br. Therefore, the gaps between crystal grains are filled up, and the recombination loss of the all‐inorganic CsPbI2Br PSCs is reduced accordingly. The champion device exhibits high open‐circuit voltage and a PCE of 1.271 V and 16.37%, respectively. This is the highest reported PCE among all‐inorganic CsPbI2Br PSCs reported so far. In addition, the stability of CsPbI2Br PSCs is effectively improved by CsBr passivation, and the device without encapsulation can retain 86% of its initial PCE after 1368 h of storage, which is beneficial for practical applications.

Silver bismuth iodide (Ag−Bi−I) as an environmentally friendly semiconductor with suitable band gap and high stability has been regarded as a potential photovoltaic material, while the reported mesoscopic devices all showed poor open circuit voltage (V oc ) of 0.5−0.6 V. Here, we successfully fabricated AgBiI 4 planar heterojunction solar cells via a solution method with a V oc approaching 0.9 V, in which 2 wt % lithium bis(trifluoromethylsulfonyl)-imide (Li-TFSI) was added into the AgI:BiI 3 precursor. The device presents a power conversion efficiency of 2.50 ± 0.20% with a V oc of 0.82 ± 0.20 V. Experimental results indicated that the readily coordinated component in the organic salt, TFSI − , could assist film growth and result in a full coverage morphology. Furthermore, double layer devices showed the carrier separation occurred in the interface of SnO 2 /AgBiI 4 . These results indicated interface extraction and film enhancement should be concerned in further improvements.

Although several studies have applied single-cell approaches to explore gene expression changes in aged brains, they were limited by the relatively shallow sampling of brain cell populations, and thus may have failed to capture aspects of the molecular signatures and dynamics of rare cell types associated with aging and diseases. Here, we set out to investigate the age-dependent dynamics of transcription and chromatin accessibility across diverse brain cell types. With EasySci, an extensively improved single-cell combinatorial indexing strategy, we profiled ~1.5 million single-cell transcriptomes and ~400,000 single-cell chromatin accessibility profiles across mouse brains spanning different ages, genotypes, and both sexes. With a novel computational framework designed for characterizing cellular subtypes based on the expression of both genes and exons, we identified > 300 cell subtypes and deciphered the underlying molecular programs and spatial locations of rare cell types (e.g., pinealocytes, tanycytes) and subtypes. Leveraging these data, we generate a global readout of age-dependent cell population dynamics with high cellular subtype resolution, providing insights into cell types that expand (e.g., rare astrocytes and vascular leptomeningeal cells in the olfactory bulb, reactive microglia and oligodendrocytes) or are depleted (e.g., neuronal progenitors, neuroblasts, committed oligodendrocyte precursors) as age progresses. Furthermore, we explored cell-type-specific responses to genetic perturbations associated with Alzheimer's disease (AD) and identify rare cell types depleted (e.g., mt-Cytb+, mt-Rnr2+ choroid plexus epithelial cells) or enriched (e.g., Col25a1+, Ndrg1+ interbrain and midbrain neurons) in both AD models. Key findings are consistent between males and females, validated across the transcriptome, chromatin accessibility, and spatial analyses. Finally, we profiled a total of 118,240 single-nuclei transcriptomes from twenty-four human brain samples derived from control and AD patients, revealing highly cell-type-specific and region-specific gene expression changes associated with AD pathogenesis. Critical AD-associated gene signatures were validated in both human and mice. In summary, these data comprise a rich resource for exploring cell-type-specific dynamics and the underlying molecular mechanisms in both normal and pathological mammalian aging.

High-efficiency organic–inorganic hybrid perovskite solar cells have experienced rapid development and attracted significant attention in recent years. However, instability to an ambient environment such as moisture is a facile challenge for the application of perovskite solar cells. Herein, 1,8-octanediammonium iodide (ODAI) is employed to construct a two-dimensional modified interface by in situ combined with residual PbI2 on the formamidinium lead iodide (FAPbI3) perovskite surface. The ODA2+ ion seems to lie horizontally on the surface of a three-dimensional perovskite due to its substitution for two FA+ ions, which could protect the bulk perovskite more effectively. The unencapsulated perovskite solar cells showed notably improved stability, which remained 92% of its initial efficiency after storing in an ambient environment for 120 days. In addition, a higher open-circuit voltage of 1.13 V compared to that of the control device (1.04 V) was obtained due to the interface energy level modification and defect passivation. A champion power conversion efficiency of 21.18% was therefore obtained with a stabilized power output of 20.64% at the maximum power point for planar perovskite solar cells.

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The toxicity of lead-based halide perovskites hampers broad application in optoelectronics. Lead-free perovskite Cs 2 AgBiBr 6 is considered a promising candidate, owing to the long carrier lifetime and great stability. However, the relatively large bandgap of 1.98 eV limits its absorption in the visible region. Herein, Fe 2+ is chosen as the dopant to alloy into Cs 2 AgBiBr 6 single crystals, and results in an absorption range broadening to ≈1350 nm, which is the longest near-infrared (NIR) response recorded among lead-free perovskites. About 1% of Fe ions are alloyed into the Cs 2 AgBiBr 6 lattice to cause lattice shrink age. Instead of narrowing the bandgap, Fe doping would introduce a new intermediate band inside the pristine bandgap of Cs 2 AgBiBr 6 to strongly absorb NIR light, as confirmed by third harmonic generation results. Moreover, considerable photogenerated carriers are produced in Fe doped Cs 2 AgBiBr 6 crystals with NIR irradiation. This work has provided a new way to extend the optical response of lead-free perovskites for NIR photodetectors and intermediate band photovoltaics.

Although the power conversion efficiency of perovskite solar cells has reached 25.5%, their long-term stability is still a barrier to commercialization. In this work, 1-methyl-3-(3′,3′,4′,4′,4′-pentafluorobutyl)imidazolium tetrafluoroborate (MFIM-2) ionic liquid and another two analogues were used as additives to study their interaction mechanism with the FAPbI 3 perovskite layer. The results reveal that MFIM-2 suppressed the formation of PbI 2 crystals during crystallization, enlarged the grain size, and reduced the defect density, which led to an increased photovoltage of 1.12 V and efficiency of 19.4%. Furthermore, the moisture stability of the solar cell devices was also improved. Devices with MFIM-2 retained above 83% of the original value after 35 days in an atmosphere with about 25% relative humidity, and the perovskite film with MFIM-2 showed no phase transition in a 10 month aging process. These results demonstrate that the additive strategy of the polyfluoroalkylated imidazolium salt is a promising way for simultaneously extending the lifetime and improving the device performance of the perovskite solar cells.