Boron Doped Nanocrystalline Film with Improved Work Function as a Buffer Layer in Thin Film Silicon Solar Cells

We investigated thin film silicon solar cells with boron doped hydrogenated nanocrystalline silicon/hydrogenated amorphous silicon oxide [p-type nc-Si:H/a-SiO _x :H] layer. First, we researched the bandgap engineering of diborane (B₂H₆) doped wide bandgap hydrogenated nanocryslline silicon (p-type nc-Si:H) films, which have excellent electrical properties of high dark conductivity, and low activation energy. The films prepared with lower doping ratio and higher hydrogen dilution ratio had higher optical gap (E_g ), with higher dark conductivity (σ_d ), and lower activation energy (E_a ). We controlled E_g from 2.10 eV to 1.75 eV, with σ_d from 1.1 S/cm to 7.59×10⁻³ S/cm, and E_a from 0.040 eV to 0.128 eV. Next, we focused on the fabrication of thin film silicon solar cells. By inserting p-type nc-Si:H film into the thin film silicon solar cells, we achieved a remarkable increase in the built-in potential from 0.803 eV to 0.901 eV. By forming p-type nc-Si:H film between SnO₂:F/ZnO:Al (30 nm) and p-type a-SiOx:H layer, the solar cell properties of open circuit voltage (V _oc), short circuit current density (J _sc), and efficiency (η) were improved by 3.7%, 9.2%, and 9.8%, respectively.