Properties of Halide Perovskite Photodetectors with Little Rubidium Incorporation

This study investigates the effects of Rb doping on the Rb-formamidinium-methylammonium-PbI3 based perovskite photodetectors. Rb was incorporated in the perovskite films with different contents, and the corresponding photo-response properties were studied. Doping of few Rb (~2.5%) was found to greatly increase the grain size and the absorbance of the perovskite. However, when the Rb content was greater than 2.5%, clustering of the Rb-rich phases emerged, the band gap decreased, and additional absorption band edge was found. The excess Rb-rich phases were the main cause that degraded the performance of the photodetectors. By space charge limit current analyses, the Rb was found to passivate the defects in the perovskite, lowering the leakage current and reducing the trap densities of carriers. This fact was used to explain the increase in the detectivity. To clarify the effect of Rb, the photovoltaic properties were measured. Similarly, h perovskite with 2.5% Rb doping increased the short-circuit current, revealing the decline of the internal defects. The 2.5% Rb doped photodetector showed the best performance with responsivity of 0.28 AW−1 and ~50% quantum efficiency. Detectivity as high as 4.6 × 1011 Jones was obtained, owing to the improved crystallinity and reduced defects.

Unravelling the Nature of a Toluene-Fumaronitrile Complex

The undertaken research allows to explain and characterize the occurrence and anomalous increase of an additional absorption band observed in the spectrum of fumaronitrile dissolved in toluene. The formation of...

Preparation, Characterization and Swelling Studies of Carboxymethyl Sago Starch Hydrogel

Carboxymethyl sago starch (CMSS) hydrogel was prepared by dissolving CMSS in HCl solution under vigorous stirring to form gel. The parameter studied were the effect of the percentage of CMSS, concentration of the acid solution, reaction time and reaction temperature to identify the optimum condition of preparation of CMSS hydrogel. 60% of CMSS in 2.0M acid solution for 12 hours reaction time at room temperature were the optimum conditions for CMSS hydrogel. The hydrogel was characterized by using Fourier Transform Infrared (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). FTIR spectrum of CMSS shows an additional absorption band at 1597 cm-1 indicating the substitution of CH2COO-Na+ group on the starch molecular chain during carboxymethylation, while the spectrum of CMSS hydrogel shows an additional sharp absorption band at 1723 cm-1 indicating that the Na in CMSS being exchanged to H from hydrochloric acid solution. SEM image of CMSS hydrogel shows pores in structure and connected to each other to form networks. TGA curve shows that the maximum rate of thermal decomposition of CMSS hydrogel is higher than CMSS at 330.22 ºC with 60.22% major weight loss. This could be due to the presence of the cross-linkages in the CMSS hydrogel. CMSS hydrogel gives high swelling degree in PBS solution at pH 7 and low swelling degree in acidic medium.

Sensitivity of Nanocrystalline Copper Sulfide/Cadmium Sulfide Heterojunction in Near-Ir Region

The photovoltaic p-n heterojunction based on thin layer of 10 nim size copper sulfide nanocrystals and evaporated cadmium sulfide film was prepared. The partial oxidation of copper sulfide nanocrystals prior the fabrication of the heterostructure results in the formation of additional absorption band in near-IR region beyond the fundamental absorption of bulk copper sulfide and cadmium sulfide. This band can be attributed to the intervalence charge transfer between copper ions in the core and in the oxidized shell. The photovoltaic effect observed in the near-IR region at ITO/nano-CuS/CdS/Au heterojunction is due to the generation of the electron-hole pairs in the CuS nanocrystalline film followed by the separation of charge carriers at the CuS/CdS junction.

Researches on the blood.—On the action of nitrites on the blood

The paper commences with a statement of the facts with which we are at present acquainted, relating to the nature and character of the blood-colouring-matter, and its relation to gases. I. The action of nitrites in modifying the colour and spectrum of blood is then described. Under the influence of nitrites, arterial blood assumes a chocolate coloration. Coincidently the bands of scarlet cruorine (oi oxidized hæmoglobin) become very faint, and an additional absorption band, occupying the same position as that of acid hæmatin, appears. The addition of ammonia to blood in which nitrites have induced the characteristic change of colour and spectrum, causes the red colour to return and gives rise to a new spectrum in which the normal blood-bands are again better defined, but accompanied by a faint and rather undefined absorption band in the orange. It appears from the experiments of the author that the change in optical properties induced by ammonia is not due to any decomposing action exerted upon the body formed under the influence of nitrites; for on neutralizing the solution to which ammonia has been added, the original spectrum is reproduced. When sulphide of ammonium, oi a reducing-solution of iron is added to a blood solution which has been acted upon by nitrites, all effects of their action disappear, and the solution again possesses the spectrum of oxidized blood-colouring-matter, although precautions have been taken to exclude atmospheric air. The continued action of the reducing-solution then leads to the reduction of the blood-colouring, matter, which when shaken with air again yields the perfectly normal spectrum of blood. It would therefore appear that when nitrites act upon the blood-colouring-matter they do not decompose it, nor thrust out oi remove the loose oxygen with which it is combined.