Preparation Of CdTe Nano-films By Electrodeposition And Properties

Cadmium telluride(CdTe)is a II-VI compound semiconductor material.Due to its band gap value(Eg=1.45ev)which matches the solar spectrum,and it has a high light absorption coefficient in the visible range(>5×10~5/cm)and electron mobility(?e=7800~8600cm~2/Vs)and other important properties are considered to be one of the most suitable materials for the light absorbing layer of solar cell devices.As we all know,it is very important to synthesize nanocrystals with a specific structure and study the properties based on this structure.In many nanomaterial preparation processes,electrodeposition method can obtain CdTe with different structures and is considered to be a suitable preparation method.This method is easy to operate,low in cost,and can be prepared in a large area.Therefore,in this paper,the CdTe thin film is prepared by electrodeposition method.The effect of deposition potential on the film is studied,and the morphology,composition,crystal structure,and photoelectrochemical properties of the film are tested and characterized.The effect of the addition of the organic additive sodium citrate on the prepared film under the acidic electrolyte system is also studied.The main work is:(1):At room temperature,a CdTe thin film with a rod-like array structure vertically grown on a vertical substrate is prepared by a constant potential electrodeposition method.Ni sheet is used as working electrode,graphite sheet is used as counter electrode,and Ag/AgCl/KCl(sat)is used as reference electrode.The electrolyte is composed of cadmium sulfate and sodium tellurite,and its pH is adjusted to 2 with sulfuric acid.At a deposition voltage of-0.5V and a deposition time of 1h,and the atomic ratio is relatively close to the stoichiometric ratio of CdTe,it is a Te-rich CdTe rod film.The film has a zinc blende structure and grows preferentially along the(111)crystal plane.(2):At room temperature,a flat CdTe thin film is prepared on the Ni substrate by electrodeposition method.In this process,the effects of deposition potential and sodium citrate concentration on the morphology,composition,crystal structure and photoelectrochemical properties of CdTe are investigated.The deposition potential is an important electrodeposition parameter,adjusting the deposition potential can adjust the ratio of elements to change the conductivity type of the film.The experiment find that in the range of-0.3V~-0.6V,with the increase of the deposition potential,the Cd/Te atomic ratio showed an increasing trend,but less than 1,indicating that the deposition potential only changed the atomic ratio of the CdTe film,and do not change its Te-rich characteristics,indicating that the P-type CdTe thin film is prepared.The deposition potential has no obvious effect on the morphology of CdTe,The deposited CdTe are all rod-shaped structures,and the crystallinity is the best at a deposition potential of-0.6V.Under the condition of this deposition potential,it is found that as the concentration of sodium citrate increased,the morphology of CdTe changed from a rod to a thin film,and the conductivity type is P type.When the concentration of sodium citrate is 0.08M,a CdTe thin film with good crystallinity and better photoelectrochemical performance is obtained.