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采用Al和CdS双靶共溅射的方法,调控Al和CdS源的沉积速率,制备出不同Al掺杂浓度的CdS∶Al薄膜.通过XRD、SEM、AFM、紫外-可见透射光谱分析、常温霍尔测试对CdS∶ Al薄膜的结构、形貌、光学和电学性质进行表征.XRD结果表明,不同Al掺杂浓度的CdS∶Al薄膜均为六方纤锌矿结构的多晶薄膜,并且在(002)方向择优生长.SEM和AFM结果表明,CdS∶Al薄膜的表面均匀致密,表面粗糙度随着Al掺杂浓度的增加略有增加.紫外-可见透射光谱分析表明,CdS∶Al薄膜禁带宽度在2.42～2.46 eV之间,随着Al掺杂浓度的增加而略微减小.常温霍尔测试结果证明,掺Al对CdS薄膜的电学性质影响显著,掺Al原子浓度3.8％以上的CdS薄膜,载流子浓度增加了3个数量级,电阻率下降了3个数量级.掺Al后的CdS薄膜n型更强,有利于与CdTe形成更强的内建场,从而提高太阳电池效率.用溅射方法制备的CdS∶Al薄膜的性质适合用作CdTe薄膜太阳电池的窗口层.

CdS∶Al thin films with different doping concentrations were deposited by controlling deposition rate of CdS and Al targets in co-sputtering process.The morphological,structural,optical,and electrical properties of as-prepared CdS∶Al films were investigated by X-ray diffraction (XRD),atomic force microscope (AFM),UV-visible absorption spectrum,and room temperature Hall-system.XRD patterns indicates that all the CdS∶Al films are polycrystalline films with hexagonal wurtzite structure and have a preferential orientation in (002) direction.The uniform and compact films can effectively be formed on insulating substrates.It is worth noting that the average grain size increases with Al doping concentration.On the other hand,the surface root-mean-square (RMS) roughness also shows slightly increase.UV-visible transmittance spectra show that the band gap of CdS∶Al film decreases slightly in the range of 2.42-2.46 eV with increasing Al doping concentration.The Hall measurements indicate that the effect of Al doping concentration on electrical property of CdS films is apparent.In comparison with the un-doped CdS thin films,the carrier concentration of CdS∶Al films increases by three orders of magnitude when the Al concentration is higher than 3.8％,while the resistivity of which decreases by three orders of magnitude.The doping level of CdS films is improved by doping with Al atoms to enhance the built-in electric field,which may realize high open voltage (V∝) for CdTe thin film solar cells.The properties of CdS∶Al film prepared by co-sputtering are suitable as a window layer of CdTe thin film solar cells.