Interfacial fixed charges and dipoles to boost carrier selectivity for crystalline silicon solar cells

With the rapid evolution of passivating contact, the carrier transport layer in crystalline silicon (c-Si) solar cells has expanded beyond the doped silicon films to non-silicon films with lower parasitic absorption and manufacturing cost. However, using the emerging carrier transport layers in direct contact with c-Si suffers from the insufficient carrier selectivity, which limits the efficiency of the device. Thus, to make such new strategies practical, it becomes particularly important to enhance the passivation quality and thus minimize the recombination losses at c-Si surfaces. By introducing interfacial fixed charges (Q_f) or dipoles on the c-Si surface, the local electric field can be tuned to affect the recombination and charge carrier transport dynamics. This perspective highlights the significance of interfacial Q_f and dipoles for carrier selectivity, and points out the challenges in a comprehensive understanding of the mechanism and precisely controlling the carrier behavior as well as the solar cell stability.