Dependence of n-cSi/MoO x Heterojunction Performance on cSi Doping Concentration

In this work, we demonstrate a strong correlation between crystalline silicon (cSi) base doping concentration and the performance of cSi/MoOx heterojunction solar cell by investigating the structure numerically based on Silvaco TCAD simulation tool and experimentally. The doping concentration of n-type cSi was scanned in the 1 × 1015 – 2 × 1016 cm-3 range. Simulation results show that utilizing highly doped cSi wafer degrades the conversion efficiency of cSi/MoOx solar cell. Efficiency of 11.16% has been obtained from simulation results for 1 × 1015 cm-3 doping concentration while this value reduces to less than 4% for wafer with a doping concentration of 2 × 1016 cm-3. These simulation results were demonstrated experimentally and n-type cSi wafers with two different doping concentrations were considered, 1 × 1015 and 5.5 × 1015 cm-3. The key concept underlying this work is to differentiate explicitly the effect of cSi doping concentration on the performance of cSi/MoOx cell, thus a simple cell design is considered where n-type cSi wafers were heavily phosphorous-doped to form (n+) at the front of the Si and thermally evaporated MoOx films with various thicknesses (<15 nm) were inserted at the rear between cSi and Al contact. In accordance to simulation results, highly doped wafer exhibited low conversion efficiency of 3.32% while using lower doped wafer significantly improves the efficiency from 3.32 to 10.9%.