Recent advancements in carrier-selective contacts for high-efficiency crystalline silicon solar cells: Industrially evolving approach

Carrier-selective crystalline silicon heterojunction (SHJ) solar cells have already reached superior lab-scale efficiencies. Besides judicious wafer thickness design, the optimal choice of passivation schemes and carrier-selective materials is essential for industry adoption. Appropriate reduction of process complexity and performance benefits through minimal recombination losses are key. Thus, along with well-designed back contacts, the development of low-temperature processable transparent passivating stacks that act as carrier-selective contacts (CSCs) is highlighted for their potential in circumventing the limited open-circuit photovoltage and contact-related losses in mainstream solar cells. In this review, effective passivation schemes deploying materials ranging from undoped metal oxides (MOs) to doped silicon are evaluated, with a focus on their significance for industrially viable passivating contact development. Passivation stack architectures with SiOx/heavily doped polycrystalline silicon (n+-/p+-poly-Si) realize the most attractive polysilicon-on-oxide (POLO) junctions and related schemes, e.g., combined with tunnel oxide passivated contact (TOPCon) and interdigitated back contact (IBC) solar cells. It is envisioned that the industrial trend is to eventually shift from the p-Si passivating emitter rear contact (PERC) and passivated emitter and rear polysilicon (PERPoly), towards TOPCon architectures, due to high manufacturing yields and compatibility with large-area metal screen printing and alternative bifacial designs.