Cho SooHo, Kim SungJoon, Jo YooShin, Kim SangHo
Department of Energy, Materials and Chemical Engineering, Korea University of Technology and Education, 31253, Republic of Korea.
J Nanosci Nanotechnol. 2019 Jul 1;19(7):3854-3858. doi: 10.1166/jnn.2019.16268.
Zinc oxide (ZnO) is a commonly used material for the front contact layer of thin film solar cells based on chalcopyrite CuInGaSe₂ (CIGS), since it satisfies the optical and electrical properties with low cost and is abundantly available. For high-performance, the front contact electrode in the CIGS solar cell should have low resistivity and high transmittance. Hence, efforts to improve ZnO's electrical and optical properties have been widely carried out. The corrosion resistance of the front contact film, however, has not been studied well. So, this paper compared the electrochemical stability of ZnO based transparent conducting oxide (TCO) films such as aluminum zinc oxide (AZO), gallium zinc oxide (GZO) and aluminum gallium zinc oxide (AGZO) grown in H₂. All films predominately grew in the (002) -axis direction and their crystallites improved with increasing H₂ ratio, reflecting the enhanced electrical properties. Hydrogen acts as a shallow donor in the -type ZnO semiconductor and increases carrier densities by forming oxygen vacancies by combining with oxygen molecules to form OH functionalities. The electrochemical corrosion resistance of prepared films showed a linear improvement with increasing hydrogen. This change was attributed to the grain morphology and size and resulting grain boundaries. Since corrosion occurs mainly at grain boundaries, corrosion resistance seems to be better with a lower density of grain boundaries, due to larger grains caused by hydrogen. Electric conductivity was better in the order of GZO > AGZO > AZO, while corrosion resistance was in the reverse order. By adding hydrogen, the electrical resistivity of AGZO improved to near GZO, and the corrosion resistance was also enhanced to near AZO.
氧化锌（ZnO）是基于黄铜矿CuInGaSe₂（CIGS）的薄膜太阳能电池前接触层常用的材料，因为它以低成本满足了光学和电学性能，且来源丰富。对于高性能的CIGS太阳能电池，前接触电极应具有低电阻率和高透射率。因此，人们广泛开展了改善ZnO电学和光学性能的工作。然而，前接触膜的耐腐蚀性尚未得到充分研究。所以，本文比较了在氢气中生长的氧化锌基透明导电氧化物（TCO）薄膜，如铝锌氧化物（AZO）、镓锌氧化物（GZO）和铝镓锌氧化物（AGZO）的电化学稳定性。所有薄膜主要沿（002）轴方向生长，并且随着氢气比例的增加，它们的微晶得到改善，这反映了电学性能的增强。氢在n型ZnO半导体中作为浅施主，通过与氧分子结合形成OH官能团来形成氧空位，从而增加载流子密度。制备薄膜的电化学耐腐蚀性随氢气含量的增加呈线性改善。这种变化归因于晶粒形态和尺寸以及由此产生的晶界。由于腐蚀主要发生在晶界处，由于氢导致晶粒较大，晶界密度较低时耐腐蚀性似乎更好。电导率按GZO > AGZO > AZO的顺序更好，而耐腐蚀性则相反。通过添加氢气，AGZO的电阻率提高到接近GZO，耐腐蚀性也提高到接近AZO。
