In this study, we focused on understanding the roles of a polysilicon (poly-Si) layer in poly-Si/SiO_x/c-Si passivating contacts. Passivating contact formation conditions were varied by changing the doping method, annealing temperature and time, polysilicon layer thickness, and polysilicon doping concentration. Our observations indicated that the roles of polysilicon are contact, in-diffusion barrier action, field effect, gettering, and light absorption. Based on the observations, a iV_OC of 741 mV was obtained. Finally, to increase J_SC with high V_OC, the polysilicon was etched after hydrogenation to reduce light absorption with high passivation quality. iV_OC was not affected by etching; moreover, by etching the polysilicon from 300 nm to 60 nm, the cell efficiency increased from 20.48% to 20.59% with increasing J_SC, constant V_OC, and fill factor.

Recently, titanium oxide has been widely investigated as a carrier-selective contact material for silicon solar cells. Herein, titanium oxide films were fabricated via simple deposition methods involving thermal evaporation and oxidation. This study focuses on characterizing an electron-selective passivated contact layer with this oxidized method. Subsequently, the SiO₂/TiO₂ stack was examined using high-resolution transmission electron microscopy. The phase and chemical composition of the titanium oxide films were analyzed using X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The passivation quality of each layer was confirmed by measuring the carrier lifetime using quasi-steady-state photoconductance, providing an implied open circuit voltage of 644 mV. UV–vis spectroscopy and UV photoelectron spectroscopy analyses demonstrated the band alignment and carrier selectivity of the TiO₂ layers. Band offsets of ~0.33 and ~2.6 eV relative to the conduction and valence bands, respectively, were confirmed for titanium oxide and the silicon interface.