Study on New Heterojunction in CIS (CuInSe_2) Thin Film Solar Cells

CuInSe_2（CIS）是一种很有前途的高效薄膜太阳能电池材料。采用CDS/CIS异质结的太阳能电池存在CdS中Cd的污染问题。本研究采用热化学气相沉积法（CVD）制备了无污染的SnO_2/CIS异质结，一般SnO_2薄膜的形成温度高于550 ℃，因此在CIS上沉积SnO_2时，CIS薄膜会发生劣化。本研究利用市售等离子体腔室，以含锡（TBT）的Ar气为源气体，通过RF电源、匹配电路和进气系统，在等离子体腔室中引入氧气，利用等离子体化学气相沉积（PECVD）技术，制备了低温生长SnO_2薄膜。沉积压力为1托。使用玻璃基板。测定了SnO_2的特性（膜厚、X射线衍射图、透过率、电子浓度和迁移率）与生长条件（电极间距、射频功率、衬底温度、TBT温度、氧气流量）的关系。在衬底温度为350 ℃、射频功率为80 W、TBT温度为140 ℃、Ar流量为120 ml/min、O2流量为100 ml/min的条件下，生长出了质量较好的多晶薄膜。在此基础上制备了SnO_2/CIS异质结二极管。这种二极管具有整流特性。然而，没有观察到光电压。这可能是由于在CVD开始时CIS表面的氧化。我们计划克服这个问题，并继续研究具有ITO，ZnO和a-Si异质结的CIS太阳能电池。

CuInSe_2 (CIS) is a promising material for efficient thin film solar cell. The solar cell using the CDS/CIS heterojunction has the Pollution problem of Cd in CdS. In this research, the preparation of pollution free SnO_2/CIS hererojunctions and its characterization have been done.In general, the SnO_2 films are formed at temperature higher than 550 C by thermal CVD, and therefore the deterioration of CIS films occur during the deposition of SnO_2 on CIS. This reason Iets us study the plasma CVD growth of SnO_2 films, by which method low temperature growth of SnO_2 films expected.The plasma CVD apparatus was constructed using the commercially available plasma chamber with the RF power generator, matching circuit and gas inlet system.As the source materials, Ar gas saturated with the tin (TBT) was fed to the reactor together with oxygen. The deposition pressure was 1 Torr. Glass substrate was used. The dependences of the characteristics of SnO_2 (film thickness, X-ray pattern, transmittance, electron concentration and mobility) on the growth conditions (distance between electrode, RF power, substrate temperature, TBT temperature, oxygen flow rate) have been determined. The good quality polycrystalline films were grown under the conditions of substrate temperature of 350ﾟC, RF power of80W, TBT temperature of 140ﾟC, Ar flow rate of 120 ml/min and oxygen flow rate of 100 ml/min. No film was grown without RF power. This indicates that the plasma plays an important role for the film growth.Based on this result, SnO_2/CIS heterojunction diode has been prepared. This diode exhibited a rectifying characteristic. However, no photovoltage was observed. This may be due to the oxidation of the surface of CIS at the beginning of the CVD. We plan to overcome this problem and to continue the research of the CIS solar cells havinig the heterojunction with ITO, ZnO and a-Si.