Zinc-tin oxide transparent conductive layers via reactive plasma deposition for silicon heterojunction solar cells

The escalating scarcity and cost volatility of indium-based transparent conductive oxides (TCOs) critically hinder the sustainable advancement of silicon heterojunction (SHJ) solar cells. In order to reduce the use of indium, developing economically friendly and having appropriate work function transparent conductive layers has become a key issue. Here, we report crystalline silicon heterojunction solar cells with reactive plasma deposition (RPD) grown Zn_xSn_1-xO transparent conductive thin films at room temperature. Meanwhile, SHJ solar cells with magnetron sputtered ICO (i.e. Ce doped In₂O₃) and reactive plasma deposition grown GZO (i.e. Ga-doped ZnO) transparent conductive layers are compared as references. The optical and electrical properties of Zn_xSn_1-xO thin films with different doping concentrations have been systematically studied. We achieved optimal optoelectronic properties of the thin film-Zn_0.17Sn_0.83O: a low resistivity (5.57 × 10⁻³ Ω cm), a high carrier mobility (27 cm²/V·s) and a proper work function similar to n-type amorphous silicon (4.32 eV). The integration of a 30 nm-Zn_0.17Sn_0.83O buffer layer between magnetron-sputtered ICO and n-a-Si:H exhibits a higher minority carrier lifetime as well as relatively higher Voc because the work function of Zn_0.17Sn_0.83O is similar to that of n-a-Si:H and the interface damage is reduced during the thin-film deposition process. The SHJ solar cell achieved an efficiency of 20.76 % (Voc = 730.48 mV, Jsc = 40.19 mA/cm², FF = 70.51 %). This work highlights RPD-grown Zn_xSn_1-xO transparent conductive layers, and their application as the buffer layer in SHJ solar cells, which will help to promote the development of the SHJ solar cell photovoltaic industry.