The phase instability and large energy loss are two obstacles to achieve stable and efficient inorganic‐CsPbI3−xBrx perovskite solar cells. In this work, stable cubic perovskite (α)‐phase CsPbI2Br is successfully achieved by Pb(Ac)2 functioning at the grain boundary under low temperature. Ac− strongly coordinates with CsPbI2Br to stabilize the α‐phase and also make the grain size smaller and film uniform by fast nucleation. PbO is formed in situ at the grain boundary by decomposing Pb(Ac)2 at high‐temperature annealing. The semiconducting PbO effectively passivates the surface states, reduces the interface recombination, and promotes the charge transport in CsPbI2Br perovskite solar cells. A 12% efficiency and good stability are obtained for in situ PbO‐passivated CsPbI2Br solar cells, while Pb(Ac)2‐passivated device exhibits 8.7% performance and the highest stability, much better than the control device with 8.5% performance and inferior stability. This article highlights the extrinsic ionic grain boundary functionalization to achieve stable and efficient inorganic CsPbI3−xBrx materials and the devices.

We report the enhanced field emission of B-doped SiC nanowires with a low turn-on field and enhanced high-temperature stability.

Built-in field and energy band alignment decide the charge separation and transportation in perovskite solar cells. Composition change in perovskites to tune the energy states is thus valuable to try. In contrast to the equivalent substitution of Pb, here trivalent Sb is for the first time incorporated into CH3NH3PbI3, with a tuned optical band gap from 1.55 to 2.06 eV. Density function theory (DFT) calculations unveil the enlarged energy band gap and n-type doping property by Sb with more valence electrons than Pb. n-Type doping by Sb elevates the quasi-Fermi energy level of the perovskite/TiO2 and promotes electron transport in the working solar cell. Thus, the doped perovskite solar cell gains a lot in photovoltage while maintaining a high photocurrent, resulting in enhanced performance of 15.6% (0.956 sun, AM1.5). The results highlight the method of n/p-type doping of perovskites by heterovalent elements and its tunability to the energy states.

We report the synthesis and anode application for sodium-ion batteries (SIBs) of WS2 nanowires (WS2 NWs). WS2 NWs with very thin diameter of ≈25 nm and expanded interlayer spacing of 0.83 nm were prepared by using a facile solvothermal method followed by a heat treatment. The as-prepared WS2 NWs were evaluated as anode materials of SIBs in two potential windows of 0.01-2.5 V and 0.5-3 V. WS2 NWs displayed a remarkable capacity (605.3 mA h g(-1) at 100 mA g(-1) ) but with irreversible conversion reaction in the potential window of 0.01-2.5 V. In comparison, WS2 NWs showed a reversible intercalation mechanism in the potential window of 0.5-3 V, in which the nanowire-framework is well maintained. In the latter case, the interlayers of WS2 are gradually expanded and exfoliated during repeated charge-discharge cycling. This not only provides more active sites and open channels for the intercalation of Na(+) but also facilitates the electronic and ionic diffusion. Therefore, WS2 NWs exhibited an ultra-long cycle life with high capacity and rate capability in the potential window of 0.5-3 V. This study shows that WS2 NWs are promising as the anode materials of room-temperature SIBs.

Perovskite solar cells as a hot research topic show the necessity of controlling the interface. In this work, an insulating alkyl chain layer is self-assembled at the perovskite/hole transport material interface, which successfully exhibits a dual function: blocking electron recombination and resisting moisture at the same time. Improved solar energy conversion efficiency and stability of the device are both achieved.