Gallium-Doped Zinc Oxide/Tungsten-Doped Indium Oxide Stacks with Enhanced Lateral Transport Capability for Efficient and Low-Cost Silicon Heterojunction Solar Cells

To decrease the series resistance in front gallium-doped zinc oxide (GZO) silicon heterojunction (SHJ) solar cells caused by high-resistivity GZO films, stack films including tungsten-doped indium oxide (IWO) films which have better lateral transport properties are used as the front transparent conductive oxide (TCO) to improve charge transport. The crystal structure and electrical and optical characteristics of GZO/IWO stacks with different thickness ratios are investigated, and the current-voltage performance of SHJ solar cells with front GZO/IWO stacks and rear GZO film are analyzed. The effective transmittance of the stacks is greater than 98% in the visible region. When the thickness of GZO/IWO is 50 nm:50 nm, the resistivity reaches 8.59 x 10-4 omega cm, which is a significantly 70% reduction compared with that of a single GZO film. Meanwhile, the power conversion efficiency is improved to 23.8%, effectively reducing the efficiency gap by approximately 0.12% compared to a single IWO transparent electrode. More effective lateral transport lowers the series resistance of SHJ solar cells. By employing stacks with lower indium content in the front TCO of SHJ solar cells, the cost can be reduced without significantly affecting the efficiency, which is important for the large-scale development of SHJ solar cells. To decrease the resistivity of gallium-doped zinc oxide (GZO) film, the GZO/tungsten-doped indium oxide stack is developed and its resistivity is significantly reduced by 70%. Consequently, fill factor of front stack silicon heterojunction solar cell is improved, and efficiency is increased by 0.56% compared with single GZO film, which is attributed to the stack with the enhanced lateral transport characteristics.image (c) 2024 WILEY-VCH GmbH