Selectivity of TiO<sub><i>x</i></sub>‐Based Electron‐Selective Contacts on n‐Type Crystalline Silicon and Solar Cell Efficiency Potential
Valeriya Titova, Jan Schmidt
Abstract
The selectivity parameter S 10 of titanium oxide (TiO x )‐based selective contacts on n‐type silicon is experimentally extracted through measurements of the specific contact resistivity ρ c and the recombination current density prefactor J 0 , both parameters measured on fully Al‐metallized samples. The contact resistivity ρ c is determined applying the Cox and Strack method and the J 0 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/SiO y /TiO x /Al contact is determined to be S 10 = 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.