Bi-doped Graphitic Carbon Nitride Nanotubes Boosts the Degradation Photocatalysis of Rhodamine B

Polymeric carbon nitride (PCN) is an emerging metal-free photocatalysts with high stability but is plagued by low photocatalytic efficiency due to the rapid charge carrier recombination behavior. Herein, Bi doped...

Surface-Passivated CsPbBr3 for Developing Efficient and Stable Perovskite Photovoltaics

All-inorganic perovskites consisting of only inorganic elements have been recently considered as highly stable semiconductors for photoactive layer of optoelectronics applications. However, the formation of high-quality thin film and trap-reduced interface has still remains an important task, which should be solved for improving the performances of all-inorganic perovskite-based photovoltaics. Here, we adopted facile method that could reduce charge-carrier recombination by depositing a passivation agent on the top surface of the CsPbBr3 all-inorganic perovskite layer. We also found that the CsPbBr3 perovskite photovoltaic prepared from surface treatment method using n-octylammonium bromide provides an improved stability in ambient environment and 1-sun illuminating condition. Therefore, the perovskite photovoltaics fabricated from our approach offered an improved power conversion efficiency of 5.44% over that of the control device without surface treatment (4.12%).

Off-axis multilayer zone plate with 16 nm × 28 nm focus for high-resolution X-ray beam induced current imaging

Using multilayer zone plates (MZPs) as two-dimensional optics, focal spot sizes of less than 10 nm can be achieved, as we show here with a focus of 8.4 nm × 9.6 nm, but the need for order-sorting apertures prohibits practical working distances. To overcome this issue, here an off-axis illumination of a circular MZP is introduced to trade off between working distance and focal spot size. By this, the working distance between order-sorting aperture and sample can be more than doubled. Exploiting a 2D focus of 16 nm × 28 nm, real-space 2D mapping of local electric fields and charge carrier recombination using X-ray beam induced current in a single InP nanowire is demonstrated. Simulations show that a dedicated off-axis MZP can reach sub-10 nm focusing combined with reasonable working distances and low background, which could be used for in operando imaging of composition, carrier collection and strain in nanostructured devices.

Are Shockley-Read-Hall and ABC models valid for lead halide perovskites?

Metal halide perovskites are an important class of emerging semiconductors. Their charge carrier dynamics is poorly understood due to limited knowledge of defect physics and charge carrier recombination mechanisms. Nevertheless, classical ABC and Shockley-Read-Hall (SRH) models are ubiquitously applied to perovskites without considering their validity. Herein, an advanced technique mapping photoluminescence quantum yield (PLQY) as a function of both the excitation pulse energy and repetition frequency is developed and employed to examine the validity of these models. While ABC and SRH fail to explain the charge dynamics in a broad range of conditions, the addition of Auger recombination and trapping to the SRH model enables a quantitative fitting of PLQY maps and low-power PL decay kinetics, and extracting trap concentrations and efficacies. However, PL kinetics at high power are too fast and cannot be explained. The proposed PLQY mapping technique is ideal for a comprehensive testing of theories and applicable to any semiconductor.