IMPROVEMENT OF ELECTRIC PROPERTIES OF ELECTRODEPOSITED CdTe FOR SOLAR CELL BY MICROSTRUCTURE CONTROL

CdTe是一种很有前途的太阳能电池材料。我们证明，水性碱性氨电解质，而不是传统的酸性硫酸盐电解质，是适合于均匀的p型CdTe层的电沉积。但是，在酸性溶液中，p型CdTe的电阻率要大于n型CdTe的电阻率。从碱性电解液中制备的CdTe层的晶粒尺寸小于从酸性介质中制备的晶粒尺寸。为了提高电沉积CdTe的电学性能，获得较大晶粒的CdTe可能是有效的。在较高温度下的电沉积是一种可行的方法。然而，在含氨碱性电解质中，在348 K下发生共沸。因此，我们开发了一种高压釜型容器，并采用了电接触沉积方法。在363 ~ 423 K的温度范围内获得了CdTe薄膜。在沉积温度的上升略有增加的Cd含量和平均微晶尺寸的CdTe。在393 K下获得了平均晶粒尺寸为19 nm的近化学计量比的CdTe层。结果表明，所沉积的CdTe层具有n型导电性，表明电解液中的氯离子进入CdTe层中形成施主能级，研究了热处理对CdTe晶粒尺寸的影响。在673 K下热处理30 min，获得了平均晶粒尺寸为33 nm的CdTe薄膜。采用电沉积和热处理方法制备的p-CdTe/ n-CdS异质结太阳能电池的能量转换效率为1.8%。

CdTe is a promisng material for solar cell applications. We demonstrated that aqueous basic ammoniacal electrolytes, instead of traditional acidic sulfate lectrolytes, are suitable for electrodeposition of uniform p-type CdTe layers. However, the resistivity of the p-type CdTe was grater than that of the n-type CdTe from the acidic bath. The grain sizes of as prepared CdTe layers from basic electrolytes are smaller than those from acidic media. To improve the electric properties of electrodeposited CdTe, it may be effective to obtain CdTe with larger grains. Electrodeposition at higher temperature is a plausible way for this purpose. In the ammoniacal basic electrolyte, however, azeotropy occurs at 348 K. Therefore, we developed an autoclave-type vessel and employed a galvanic contact deposition method. CdTe layers were obtained at a temperature range from 363 K to 423 K. The rise in the deposition temperatures slightly increased the Cd contents and mean crystallite size of CdTe. A near stoichiometric CdTe layer with mean crystallite size of 19 nm was obtained at 393 K.The effect of chloride ions was investigated. The asdeposited CdTe layer had an n-type conduction, suggesting that chloride ions in the electrolyte became incorporated into the CdTe layer and formed the donor level.The effect of thermal treatment on the grain size of CdTe was examined. CdTe layer with mean crystallite size of 33 nm was obtained by at 673 K for 30 min. The energy conversion efficiency of the p-CdTe/ n-CdS heterojunction solar cell prepared by electrodeposition and the thermal treatment was 1.8 %.