Optimization of a Solution-Processed TiO/(n)c-Si Electron-Selective Interface by Pre- and Postdeposition Treatments.

Developing a vacuum-free and low-temperature deposition technique for dopant-free carrier-selective materials without sacrificing their performance can reduce the fabrication cost and CO footprint of silicon heterojunction (SHJ) solar cells. In this contribution, to activate the full capacity of the solution-processed TiO as an electron-selective passivation contact, the effects of various pre- and postdeposition treatments on the passivation quality and contact resistivity are investigated simultaneously. It is demonstrated that the electrical properties of a thin TiO layer spin-coated on an n-type silicon substrate can be remarkably improved through tailor-made pre- and postdeposition treatments. A notable low surface recombination velocity (SRV) of 6.54 cm/s and a high implied open-circuit voltage (i) of 706 mV are achieved. In addition, by inserting a 1 nm LiF buffer layer between TiO and Al metal contact, a low contact resistivity (ρc) of 15.4 mΩ·cm is extracted at the n-Si/SiO/TiO heterojunction. Our results bring the solution-processed TiO electrical properties to a level on par with those of state-of-the-art pure TiO layers deposited by other techniques. Chemical and electrical characterizations elucidate that the improved electrical properties of the investigated Si/SiO/TiO heterojunction are mediated by the concomitant involvement of chemical and field-effect passivation.