Improving the efficiency of rear emitter silicon solar cell using an optimized n-type silicon oxide front surface...

Optical and electrical characteristics of n-type nano-crystalline-silicon oxide (n-µc-SiO:H) materials can be varied to optimize and improve the performance of a solar cell. In silicon heretojunction (SHJ) solar cells, it can be used to improve carrier selectivity and optical transmission at the front side, both of which are vitally important in device operation. For this purpose, the n-µc-SiO:H was investigated as the front surface field (FSF) layer. During film deposition, an increased CO₂ flow rate from 0 to 6 sccm resulted in changes of crystalline volume fractions from 57 to 28%, optical band-gaps from 1.98 to 2.21 eV, dark conductivities from 7.29 to 1.1 × 10^-5 S/cm, and activation energies from 0.019 to 0.29 eV, respectively. In device applications, a minimum optical reflection was estimated for the FSF layer that was fabricated with 4 sccm CO₂ (FSF-4), and therefore obtained the highest external quantum efficiency, although short circuit current density (J_sc) was 38.83 mA/cm² and power conversion efficiency (PCE) was 21.64%. However, the highest PCE of 22.34% with J_sc = 38.71 mA/cm² was observed with the FSF prepared with 2 sccm CO₂ (FSF-2), as the combined opto-electronic properties of FSF-2 were better than those of the FSF-4.