Tantalum-Doped Tin Oxide Rear Reflector for Efficient and Low-Cost Silicon Heterojunction Solar Cells

Abstract

Promoting infrared (IR) response is crucial to boost the short-circuit current density (J_SC) of thinner silicon heterojunction (SHJ) solar cells. Herein, tantalum-doped tin oxide (TaTO) film is not only a transparent conductive film but also used as rear reflector stacked with multiple-doped indium oxide (IMO) to promote the IR quantum efficiency of SHJ solar cells. Stack films (IMO/TaTO) are prepared and their structural and optical–electrical properties were studied. IMO/TaTO stack film is a layer of polycrystalline IMO film covered by amorphous TaTO film. Given the low surface roughness of amorphous film, the IMO/TaTO stack films show higher reflectance than single-IMO film in IR region. The carrier concentration of IMO/TaTO stack film is 1.06 × 10²⁰ cm⁻³, one third of IMO films, leading to low absorption loss in IR region. Therefore, a J_SC gain of 1.55%_rel for industrial SHJ solar cells with rear IMO/TaTO films is acquired due to improvement of IR response. Finally, an average power conversion efficiency gain of 0.27%_abs is come through, providing that stacks with less indium content in the rear side of SHJ solar cells is feasible to enhance the efficiency of SHJ solar cells.