(Invited, Digital Presentation) Advanced Passivating Contacts for Silicon Photovoltaics

Abstract

Carrier selective passivating contacts, which provide dual functions of surface defect passivation and extracting one type of charge carriers, is a key enabler for high efficiency Si solar cells. Here we introduce two passivating contact materials developed in our lab: one is the hydrogenated nanocrystalline silicon (nc-Si:H) and the other is the metal-oxide (non-silicon) material. For the nc-Si:H, it is demonstrated that the use of the (p)nc-Si:H/(i)a-Si:H stack instead of the conventional (p)a-Si:H/(i)a-Si:H in silicon heterojunction solar cells provides not only a mitigation of the parasitic absorption loss but also improvements in passivation and electrical contact properties. This results in an efficiency increase by 0.3-0.6% absolute compared to our reference cell, and a best cell efficiency of 23.5%. For metal-oxide material, we have developed an atomic-layer-deposited titanium oxide (TiOx) that functions as an efficient and transparent hole-selective passivating contact without using buffer layer, leading to the proof-of-concept solar cells with efficiencies above 20%. An example of applying the developed contact material as a recombination junction layer of the perovskite/Si tandem solar cell will be presented.