Optimizing transparent conductive Al-doped ZnO thin films for SiNx free crystalline Si solar cells

Abstract

Al-doped ZnO (AZO) thin films with resistivity of 6.6 × 10−4 Ω cm were prepared by introducing H2 in DC magnetron sputtering atmosphere. The Hall Effect measurement demonstrates that a part of the hydrogen atoms act as shallow donors while others act as neutral scattering impurities. Only proper H2 partial pressure decreases the resistivity to the lowest value. The properties of SiNx free crystalline Si (c-Si) solar cells were improved when AZO thin films were applied. The films served as both anti-reflection (AR) coatings and front electrode assistance. Ensuring an outstanding AR effect and a low sheet resistance, the thickness of the films was optimized in order to reduce the optical absorption, and thus effectively increase the short circuit current density (Jsc). The influence of the films versus different Ag fingers and emitter sheet resistance was investigated. The results showed that the Jsc was improved apparently (at least by 0.7 mA/cm2), while the fill factor was enhanced obviously from 62 to 70 % and from 73 to 75 %, respectively, which depended on the initial series resistance.