Nonlinear Doping, Chemical Passivation and Photoluminescence Mechanism in Water-Soluble Silicon Quantum Dots by Mechanochemical Synthesis

A series of boron- and phosphorus-doped silicon wafers are used to prepare a series of doped silicon nanocrystals （nc-Si） by high-energy ball milling with carboxylic acid-terminated surface. The sizes of the nc-Si samples are demonstrated to be 〈 S nm. The doping levels of the nc-Si are found to be nonlinearly dependent on the original doping level of the wafers by x-ray photoelectron spectroscopy measurement. It is found that the nonlinear doping process will lead to the nonlinear chemical passivation and photoluminescence （I3L） intensity evolution. The doping, chemical passivation and PL mechanisms of the doped nc-Si samples prepared by mechanochemical synthesis are analyzed in detail.

Full-scale chemical and field-effect passivation:21.52% efficiency of stable MAPbI_(3) solar cells via benzenamine modification

Organic-inorganic metal halide perovskite solar cells have achieved high efficiency of 25.5%.Finding an effective means to suppress the formation of traps and correlate stability losses are thought to be a promising route for further increasing the photovoltaic performance and commercialization potential of perovskite photovoltaic devices.Herein,we report a facile passivation model,which uses a multi-functional organic molecule to simultaneously realize the chemical passivation and field-effect passivation for the perovskite film by an upgraded anti-solvent coating method,which reduces the trap states density of the perovskite,improves interface charge transfer,and thus promotes device performance.In addition,the hydrophobic groups of the molecules can form a moisture-repelling barrier on the perovskite grains,which apparently promotes the humidity stability of the solar cells.Therefore,the optimal power conversion efficiency(PCE)of perovskite solar cells after synergistic passivation reaches 21.52%,and it can still retain 95%of the original PCE when stored in-40%humidity for 30 days.Our findings extend the scope for traps passivation to further promote both the photovoltaic performance and the stability of the perovskite solar cells.

Few-layer MoS2 grown by chemical vapor deposition as a passive Q-switcher for tunable erbium-doped fiber lasers

We report an erbium-doped fiber laser passively Q-switched by a few-layer molybdenum disulfide（MoS2） saturable absorber（SA）.The few-layer MoS2 is grown by the chemical vapor deposition method and transferred onto the end-face of a fiber connector to form a fiber-compatible MoS2 SA.The laser cavity is constructed by using a three-port optical circulator and a fiber Bragg grating（FBG） as the two end-mirrors.Stable Q-switched pulses are obtained with a pulse duration of 1.92 μs at 1560.5 nm.By increasing the pump power from 42 to 204 mW,the pulse repetition rate can be widely changed from 28.6 to 114.8 kHz.Passive Q-switching operations with discrete lasing wavelengths ranging from 1529.8 to 1570.1 nm are also investigated by using FBGs with different central wavelengths.This work demonstrates that few-layer MoS2 can serve as a promising SA for wideband-tunable Q-switching laser operation.

Atomistic Insights into Oxidation of Chemical Passivated Silicon(100)Surface:Reactive Molecular Dynamic Simulations

Main observation and conclusion In this paper,a series of ReaxFF molecular dynamic simulations were performed to study the oxidation of chemical passivated silicon(100)surface,which was terminated with different n-alkyl chains.The simulated results showed that the oxidant species diffuse into Si substrate through peroxy-like structures during the oxidation process.During the oxidation process,the Si-alkyl(Si-C)covalent bond was stable and there is no occurrence of decomposition of the n-alkyl chains.In addition,the existence of n-alkyl monolayers on silicon surface did not change the initial reaction pathway of the oxidation process.The simulations indicated that the chemical passivation mechanism includes two parts,one is about the Si-C covalent bond occupying the active site of the reaction on Si(100)surface,and the other is about the oxygen penetrating Si-alkyl layers.The simulations also indicated that the chemical passivation of Si-alkyl is better for longer alkyl chains,which is consistent with the experimental observation.Our results have investigated the oxidation of chemical passivated silicon(100)surface at the atom level,which is helpful to comprehend the manufacture of semiconductor devices like metal-oxide-semiconductor(MOS)devices in the experiments.