Hydrothermal Synthesis Of Layered Cu-based Chalcogenides And Their Photoelectric Properties

As an important sort of solar cell materials,chalcogenides have attracted a wide range of research interests due to their diverse structure,suitable bandgap,and high opt-ical absorption coefficient.However,the known chalcogen compounds with excellent photoelectric properties are mostly limited to chalcopyrite and its derivatives,and the constituent elements are highly toxic and low reserves with high preparation costs.On the other hand,compared with the solid phase method,the hydrothermal method can obtain crystals with fewer defects and higher crystallinity,and the preparation process is simple while the cost is low.Therefore,the use of hydrothermal method to produce new type of layered chalcogenides with high efficiency,low consumption,rich composition of elements,and environment-friendly must be very meaningful work.In this paper,three kinds of layered copper-based chalcogenide compounds were synthesized by hydrothermal method,and the reaction conditions(reaction material types,mineralizer concentration,reaction time and reaction temperature,etc.)were se-lected to prepare samples with higher crystallinity and purity and higher yields.Their structures,morphologies and photoelectric properties were also explored.The specific work of the thesis mainly includes the following aspects:(1)The sheet-like monocrystalline BiOCuQ(Q = S and Se)systems were synthe-sized by hydrothermal method and their photoelectric properties were studied.XRD analysis demonstrated that different selenium sources have an influence on the growth orientation of BiOCuSe.The results of photoelectric tests(The photocurrent densities of BiOCuSe and BiOCuS are about 10 ?A/cm2 and 5.5 ?A/cm2,respectively,and the pho-toelectric response times are about 2.5 s and 3 s,respectively)showed that the substitu-tion of S element with Se element has a certain enhancement effect on the photoelectric properties.Preliminary judgment may be that Se is less non-metallic than S,and the ra-dius of Se is larger than that of S,which results in BiOCuSe's layer spacing larger than these of BiOCuS,which makes BiOCuSe more rapid in the carrier transfer rate and slower in recombination rate,thus showing more significant photoelectric properties than BiOCuS;(2)A novel layered flaky monocrystalline chalcogenide,K2COCu3S4,was synthe-sized by hydrothermal method.XRD showed that with the increasing of the S content in the reaction system appropriately,the dissolution and reaction of sulfur and transition metal ions in the reaction solution can be promoted,and samples can be prepared with higher crystallinity.The photoelectric property test indicated that the sample had a higher photocurrent density(about 5 mA/cm2)under visible light irradiation,which proved to be degenerate semiconductor.(3)The KMnCuS2 monocrystallines with high crystallinity and purity were synthe-sized by hydrothermal method.The photoelectric properties test showed that the sample had obvious photocurrent(10 ?A/cm2 or so)and short photoresponse time(?1 s).The initial speculation may be that the substitution of K+ and the substitution of Mn2+changed the electronic structures and enlarged the interlayer spacing of KMnCuS2,thus promoted the transmission of K+ and electrons between the interlayers,and improved the conductivity of the sample,which makes the KMnCuS2 sample showed excellent pho-toelectric properties.