Selectivity of TiOx-Based Electron-Selective Contacts on n-Type Crystalline Silicon and Solar Cell Efficiency Potential

Abstract

The selectivity parameter S10 of titanium oxide (TiOx)-based selective contacts on n-type silicon is experimentally extracted through measurements of the specific contact resistivity ρc and the recombination current density prefactor J0, both parameters measured on fully Al-metallized samples. The contact resistivity ρc is determined applying the Cox and Strack method and the J0 values are extracted using dynamic infrared lifetime mapping, allowing for contactless lifetime measurements on fully metallized silicon samples in contrast to conventionally applied lifetime measurement techniques. The highest selectivity after annealing of an n-Si/SiOy/TiOx/Al contact is determined to be S10 = 11.6, which corresponds to a maximum achievable efficiency of 24.1% for this type of electron-selective contact. The maximum selectivity is achieved after low-temperature annealing at 500 °C or through a contact-firing step at a set-peak temperature of 820 °C in an industrial conveyor-belt furnace, as used in today's commercial solar cell production. © 2021 The Authors. physica status solidi (RRL) Rapid Research Letters published by Wiley-VCH Gmb