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.
Although the replacement of aromatic rings with C(sp3)-rich isosteres has proven essential for improving the reactivity of drug candidates, the development of aza-arene-related isosteres, especially for privileged quinolines, remains limited due to the lack of efficient and controllable synthetic methods. Herein, we report a cost-effective Cu(I)-catalyzed chemodivergent trifunctionalization protocol for unactivated alkenes, which leverages the integrated versatile chemical reactivity of N,N-difluoroarylsulfonamides. This strategy enables the de novo synthesis of two types of topologically complex bridged sultams that are otherwise difficult to access using existing methods. The synthetic utility of our approach is demonstrated through the late-stage functionalization of biologically relevant targets and the synthesis of 15N-labeled molecules. More essentially, preliminary biological studies have identified that the synthesized bridged sultams serve as three-dimensional isosteres of quinoline, exhibiting enhanced bioactivity for cancer treatment. Comprehensive mechanistic studies further elucidate this reaction pathway.
Two-dimensional (2D) materials hold great promise for next-generation optoelectronic devices, with photogenerated charge carrier transport being critical to their performance. However, the influence of photoexcitation-induced commensurate lattice thermal effects on surface charge carrier dynamics is poorly understood. Traditional photon-pump/photon-probe methods have constraints in capturing the subtle yet critical surface dynamics, especially for these ultrathin materials due to challenges in spatial resolution and penetration depth. In this study, we utilized scanning ultrafast electron microscopy (SUEM), a technique that offers unparalleled sensitivity to surface phenomena that are entirely inaccessible through other methods. Our findings reveal a similar to 1.4% negative thermal expansion at elevated temperatures, inducing internal strain that modifies the electronic structure and significantly enhances surface carrier transport, resulting in an order-of-magnitude improvement in photodetection performance. Moreover, we demonstrate that photoinduced charge carrier diffusion occurs predominantly within the first tens of picoseconds after photoexcitation, a regime characterized by thermal excitation resulting from carrier-phonon interactions. These results establish a direct link among lattice thermal expansion, carrier dynamics, and optoelectronic performance.
