RESUMEN
All-inorganic cesium lead bromide quantum dots (CsPbBr3 -QD) compounds are potential candidates for optoelectronic devices, because of their excellent fluorescence luminescence and thermal stability. However, the many heterojunction interfaces and large band gap induce the low power conversion efficiency in the CsPbBr3 -QD heterojunction, limiting its practical applications. Hereby, in combination with the pressure regulation and TiO2 /CsPbBr3 -QD heterojunction, the interface interaction within the heterojunction can be enhanced and the band gap can be narrowed. The pressure-induced OâTiâO bond softening and PbBr6 octahedron stiffening at the interface region significantly enhance the interface interactions that are favorable to the carrier transport. Compared with CsPbBr3 -QD, the atomic interaction between Pb and Br of TiO2 /CsPbBr3 -QD heterojunction can be dramatically enhanced at high pressures, leading to increased band gap narrowing rate by two times, which is useful to widen the absorption spectrum. The fluorescence intensity increases by two times. Compression increases the photocurrent and maintains it after the pressure is released, which is due to the enhanced interface interaction induced by the high pressure. The findings provide new opportunities to adjust the physical properties of perovskite heterogeneous structures, and have important applications in the field of new-generation photovoltaic devices.
RESUMEN
Superatomic crystals are a class of hierarchical materials composed of atomically precise clusters assembled via van der Waals or covalent-like interactions. Au6Te12Se8, an all-inorganic superatomic superconductor exhibiting superatomic-charge-density-wave (S-CDW), provides the first platform to study the response of its collective quantum phenomenon to the external pressure in superatomic crystals. We reveal a competition between S-CDW and superconductivity in an ultra-narrow pressure range. Distinct from conventional CDW ordering, S-CDW shows the lowest threshold (0.1 GPa) toward external pressure that is 1-2 orders of magnitude lower than other atomic compounds. Prominently, a second superconducting phase emerges above 7.3 GPa with a threefold enhancement in the transition temperature (Tc) to 8.5 K, indicating a switch of the conduction channel from the a- to b-axis. In situ synchrotron diffractions and theoretical calculations reveal a pressure-mediated mesoscopic slip of the superatoms and a 2D-3D transition of the Fermi surface topology, which well explains the observed dimensional crossover of conductivity and re-entrant superconductivity.
RESUMEN
The eco-friendly properties enable two-dimensional (2D) Cu-based perovskites as ideal candidates for next-generation optoelectronics, but practical application is limited by low photoelectric conversion efficiency because of poor carrier transport abilities. Here, we report enhanced structural stability of 2D CuBr4 perovskites under compression up to 30â GPa, without obvious volume collapse or structural amorphization, by inserting organic C6 H5 CH2 NH3 (PMA) groups between layers. The band gap value of (PMA)2 CuBr4 can be effectively tuned from 1.8 to 1.47â eV by employing external pressures, leading to a broadened absorption range of 400-800â nm. Notably, we successfully detected photoconductivity of the photoresponse at pressures from 10 to 40â GPa; the maximum value of 5×10-3 â S cm-1 is observed at 28â GPa, indicating potential applications for high performance photovoltaic candidates under extreme conditions.
