三元多晶硫属化物CuInX_2 (X= Se，S)的光电化学研究

CuInS_2、CuInSe_2等三元半导体化合物具有光电转化效率较高，稳定性好等优点，近来在光电转化方面很受重视。本文总结了CuInSe_2、CuInS_2等化合物在光电化学转化方面的大部分工作。以及概要地介绍了半导体光电化学原理。采用电流沉积和喷涂热解的方法成功地制备了CuInSe_2和CuInS_2多晶薄膜，并对它们的光电化学性能进行了较详细的研究。我们所用的电沉积溶液是1.4mM CuCl_2 + 10mM InCl_3 + 4.2mM SeO_2 + 10mM KCl (pH = 1.6～1.7)，控制电位-0.8 V (v.s.SCE)，在荃底钛上得到了结构为黄铜矿的CuInSe_2藻膜。将薄膜退火后与多硫溶液构成PEC，在AM1的光照条件下，得到开路光电压220mV。短路光电流～5mA cm~(-2)，光电转化效率为0.23%。薄膜中Cu和In的比例由电沉积溶液的组成控制；薄膜中Cu/In < 1，则薄膜是n型光电响应，Cu/In > 1，则呈弱的P型响应。退火对薄膜的结构和光电活性影响很大，最佳的退火温度是350 ℃，用光谱响应的方法测出了CuInSe_2薄膜的禁带宽度为0.98 eV，与太阳光谱相匹配。用MoH-SchoHky方法和开路光电压与光强的关系求出了薄膜电极在多硫溶液中的平带电位，从而确定了CuInSe_2半导体的能带结构。CuInSe_2薄膜电极在多硫溶液中稳定性较好，CuInSe-多硫溶液PEC在短路状态、AM1光照强度下连续放电三小时，光电流没有变化。荃底物质和电沉积溶液对薄膜的光电活性的影响表明，CuInSe_2薄膜与荃底的接触好坏极大地影响了PEC的光电流及光电转化效率。另外，CuInSe_2薄膜电极在铁氯溶液中的光活性得到了改善，然而其稳定性却不理想。喷涂热解法制备CuInS_2新用的溶液为CuCl_2、InCl_3和硫脲的水溶液。制备的薄膜由X射线衍射分析确定其结构为闪锌矿型。在AM1光照条件下，CuInS_2-多硫溶液PEC给出开路光电压为170mV，短路光电流为3.8mA cm~(-2)。由光谱响应法测得CuInS_2薄膜的禁带宽度为1.25eV，比单晶CuInS_2的标准值1.55eV小得多。CuInS_2-多硫溶液PEC在短路状态、AM1光照强度下放电一小时，光电流下降近一半，可见，CuInS_2薄膜电极稳定性较差。CuInSe_2 thin films were successfully prepared by electrodeposition from an aqeuous solution of CuCl_2, InCl_3 and SeO_2 on Ti substrates. The as-deposited layers were annealed in N_2 or Ar atmosphere at 300-350 C in about 30 minutes. X-ray diffraction analyses showed that the films were chalcopyrite structure. Microprobe analyses of the annealed layers showed that the proportion of Cu, In and Se in the layers was approximately 1:1:2. Photoelectrochemical characterization was carried out in a polysulfide electrolyte. We found a clear correlation between the conductivity type and the Cu/In ratio of the layers: for Cu/In > 1, the layers were generally p-type, otherwise n-type layers were found. The n-type thin film has a remarkable photoresponse: under AM1 condition, the CuInSe_2-polysulphide PEC gives an Open Circuit Photovoltage (Uoc) of about 220 mV and a Short Circuit Photocurrent (Jsc) of about 5.3 mA/cm~2, the efficiency of the cell is about 0.23%. The band gap (Eg) of the films is about 0.96 eV. We found that the electroplated CuInSe_2 thin films were very stable in the polysulfide solution. CuInS_2 thin films were prepared by spray pyrolysis. The films were characterized by XRD which gives the Zinc blende CuInS_2 pattern. The CuInS_2-polysulphide PEC gives an Uoc value of 170 mV and a Jse of 3.8 mA/cm~2. The CuInS_2 thin film has an Eg value of 1.25 eV, much smaller than the band gap of the single crystal CuInS_2 which has the value of 1.55 eV. The CuInS_2 thin films are not stable in polysulphide solution