Near-unity quantum yield in zero-dimensional lead-free manganese-based halides for flexible X-ray imaging with high spatial resolution

Low-dimensional luminescent lead-free metal halides have received substantial attention due to their unique optoelectronic properties. Among them, zero-dimensional (0D) manganese (II)-based metal halides with negligible self-absorption have emerged as potential candidates in X-ray scintillators. Herein, we for the first time report a novel lead-free (TBA)2MnBr4 single crystal synthesized via a facile solvent evaporation method. In this crystal, [MnBr4]2− units are isolated by large TBA+ organic cations, resulting in a unique 0D structure. The prepared manganese-based crystals exhibit a bright-green emission centered at 512 ​nm with a high photoluminescence quantum yield (PLQY) of 93.76% at room temperature, originating from the 4T1–6A1 transition of Mn2+. Apart from their outstanding optical performance, the crystals also show excellent stability and can maintain 94.4% of the initial PLQY even after being stored in air for 90 days. Flexible (TBA)2MnBr4 films prepared as X-ray imaging scintillators exhibit a low detection limit of 63.3 nGyair/s, a high light yield of 68000 ​ph/MeV, and a high spatial resolution of 15.4 ​lp/mm. Thus, this work not only enriches the family of lead-free metal halides but also expands the application of manganese (II)-based halides in flexible X-ray scintillators

Simultaneous Passivation of Bulk and Interface Defects with Gradient 2D/3D Heterojunction Engineering for Efficient and Stable Perovskite Solar Cells

© 2022 American Chemical Society.Minimizing bulk and interfacial nonradiative recombination losses is key to further improving the photovoltaic performance of perovskite solar cells (PSC) but very challenging. Herein, we report a gradient dimensionality engineering to simultaneously passivate the bulk and interface defects of perovskite films. The 2D/3D heterojunction is skillfully constructed by the diffusion of an amphiphilic spacer cation from the interface to the bulk. The 2D/3D heterojunction engineering strategy has achieved multiple functions, including defect passivation, hole extraction improvement, and moisture stability enhancement. The introduction of tertiary butyl at the spacer cation should be responsible for increased film and device moisture stability. The device with 2D/3D heterojunction engineering delivers a promising efficiency of 22.54% with a high voltage of 1.186 V and high fill factor of 0.841, which benefits from significantly suppressed bulk and interfacial nonradiative recombination losses. Moreover, the modified devices demonstrate excellent light, thermal, and moisture stability over 1000 h. This work paves the way for the commercial application of perovskite photovoltaics.11Nsciescopu

Self‐Formed Multifunctional Grain Boundary Passivation Layer Achieving 22.4% Efficient and Stable Perovskite Solar Cells

The deep-level defects at grain boundary (GB) result in serious trap-assisted non-radiative recombination. Moreover, the degradation of perovskite films is preferentially triggered by the attack of GBs by water and/or oxygen. Therefore, it is urgently needed to develop a multifunctional GB tailoring strategy to address the abovementioned issues. Herein, a self-formed multifunctional GB passivation strategy is reported, where an ultrathin GB passivation layer is in situ constructed via incorporating K2SO4 into perovskite precursor solution. The self-formed GB passivation layer plays multiple functions, including crystallization improvement, defect passivation, and moisture resistance. The GB manipulation strategy endows perovskite films reduced defect density, boosted carrier lifetime, and thus suppressed non-radiative recombination, which contributes to efficiency enhancement from 20.39% to 22.40%. The GB tailoring approach makes the unencapsulated target device exhibit no degradation while the control device degrades to 93% of its initial power conversion efficiency after 1200 h ambient exposure with a relative humidity of 10–20%. The modified device maintains 98% of its original efficiency after aging at 60 °C for 1200 h, whereas only 89% for the control device. Herein, the importance of developing an in situ GB modification strategy in enhancing performance of perovskite photovoltaics is highlighted.11Nsciescopu

Identification of a mosquitocidal toxin from Bacillus thuringiensis using mass spectrometry

The Bacillus thuringiensis strain S2160-1 has previously been identified as being highly toxic to mosquito larvae and a viable alternative to strains currently used commercially to control these insects. A PCR approach had identified the presence of four putative insecticidal toxin genes (cry30Ea, cry30 Ga, cry50Ba and cry54Ba) in this strain, but did not identify the genes that encoding three of the main crystal toxin proteins of size 140 and 130 and 30 kDa. In this study we used mass spectrometry to identify the 130 kDa toxin as a rare Cry4 toxin (Cry4Cb3). The gene encoding this toxin was cloned and expressed and the toxin shown to have mosquitocidal activity against Culex quinquefasciatus