Preparation Of NiTe Thin Films And Their Application In CdTe Solar Cells

The goal of the solar cells is to cut down the cost and improveefficiency since from studying the solar cells. Now, the application ofCdTe/CdS solar cells is considered to be the most hopeful path to preparethe next generation solar cells to get the goal. Nickel foil is used assubstrate in ‘substrate configuration’ CdTe/CdS solar cells, which canreduce the cost. And the flexible cells are expected to commercialproduction.Tellurium (Te) is a P-type semiconductor material. Telluride nickel(NiTe) is an important intermetallic compound.There is no report aboutNiTe is used as back electrod which is prepared by calcinating theas-prepared Te thin film on Ni substrate. In this paper，the preparation ofNiTe and the application in CdTe/CdS solar cells are studied. And someworthy results are presented.The main work is as follows:(1) The simple and low-cost electrochemical method was used to synthesize Te film on a Ni substrate in sodium tellurite acidic solutionsystem for the first time. Cyclic voltammetry was used to study theelectrochemical reactions in the electrolyte solution. At the depositionpotential of-0.30V, the high-density vertically tellurium (Te) pillars filmwas synthesized. The structural, morphology, optical and electricalproperties of as-prepared thin films were examined by XRD, FESEMTEM and SAED. The results show Te is single crystalline with hexagonalstructure. The average diameter and length of the Te pillars are200nmand450nm, respectively.(2) A simple method was used to prepare NiTe at350oC for30min.Te film (Te source) was pre-deposited on Ni substrate (Ni source) byelectrochemical deposition method. As-prepared Te thin film wastransformed into NiTe by thermal diffusion method. The effect of variousannealing temperatures on NixTe structures was studied. In our study, theheat treatment makes the material change (Teâ†'Ni3Te2â†'NiTeâ†'NiTe2/Ni2.86Te2). The electrical properties of Ni/NixTe samples show thatthey have already formed ohmic contacts from I-V curves. And Ni/NiTeshows smaller contact resistance than other samples. The electricalproperties of Ni/NixTe suggest their potential application in solar cells onflexible Ni substrate.(3) Cadmium Telluride (CdTe) semiconductor thin films werefabricated on flexible Ni foil substrates using radio-frequency (RF) magnetron sputtering method under different substrate temperatures. Thecrystal structure and properties of the prepared functional thin films werecharacterized with series analysis technologies. The characterizationresults revealed that Nickel Telluride (NiTe) phase formatted at theinterface of CdTe and Ni substrate when substrate temperature (Ts) is450oC. Specially, XRD results demonstrated that NiTe/CdTe films could alsobe obtained by pre-depositing Te film on Ni and reducing Tsto350oC.The investigation on optical and photoelectrochemical (PEC) propertiesof the products illustrated that compact NiTe/CdTe films had improvedthe absorption in the visible region. Furthermore, PEC measurementsindicated that Ni/NiTe/CdTe photoelectrode can have a promisingapplication in photovoltaic devices.(4) CdS and ITO were prepared on the surface of Ni/NiTe/CdTe/bychemical bath deposited method and magnetron sputtering method. AndCdTe/CdS thin film solar cell module was fabricated. In preparing of CdS,the aqueous solution contain of chromium chloride，thiourea, ammoniumchloride and ammonia was used as precursors. The reaction temperatureand time were75oC and20min, respectively. The deposited condition ofITO is20sccm,1Pa,300oC，200W,5min. The optoelectronic test ofthe solar cell modules were carried out. The highest photoelectronicparameter values of the CdTe/CdS solar cell were Jsc=2.91mA/cm2, Voc=594mV, FF=0.33, and η=0.56%. Compared to the CdTe/CdS solar cell module without pre-deposited Te thin film (without NiTe interlayer),energy conversion efficiency value increased by115%. The resultsshowed that the NiTe, which was used as back electrod, improved thephotoelectric conversion efficiency of the flexible CdTe/CdS solar cells.And by further optimization of preparation parameters, there isconsiderable room for improvement in the efficiency.