Status and perspectives of transparent conductive oxide films for silicon heterojunction solar cells

Efficiently harvesting solar energy into electricity via photovoltaic devices (also called solar cells) exhibits a feasible way to tackle challenging energy supply. Over the past decades, crystal silicon (c-Si) is still the dominant material for photovoltaic manufacture, benefiting from its nearly ideal optical bandgap, abundant, and mature semiconductor technology. Up to now, the power conversion efficiency of single-junction c-Si solar cells with heterojunction structures has been boosted to over 26%, approaching its theoretical maximum efficiency. On the other hand, a trade-off of the cost/output power of heterojunction cells is still an obstacle to its expanding market share. Being different from any previous scalable c-Si photovoltaic generations, the heterojunction cell features uniquely indispensable transparent conducting oxide (TCO) layers integrating a low-temperature annealing metal paste. Its unique electrode requirement is still the dominant factor to determine its rate of exposure mass manufacture. In this review, the field of TCO development of silicon heterojunction (SHJ) solar cells is overviewed firstly. Furthermore, different TCO choices for SHJ solar cells are discussed. Finally, future research directions, challenges, and potential solutions are summarized and looked forward. To conclude, we discuss what has been taken for the TCO application for SHJ solar cells in the mass market.