The benefit of using p-a-SiOxCy:H as double window layers in hydrogenated amorphous silicon solar cells: Correlation of simulation and experiment

Abstract

By using AMPS-1D simulation program, we have simulated and compared two experimental p-i-n devices. One with p-type window and buffer layers based on hydrogenated amorphous silicon oxide (p-a-SiOx:H) and the other with two p-a-SiOxCy:H layers based on hydrogenated amorphous silicon oxycarbide.The numerical results showed that, an incorporation of the p-a-SiOxCy:H layer instead of the p-a-SiOx:H layer, as window layer reduces the value of holes front contact barrier height (φh) and as buffer layer leads to a smaller values of conduction band (ΔEC) and valence band (ΔEV) offsets. In one hand, the ΔEV low value minimizes the recombination of photogenerated holes at the i/p interface. In the other hand, low value of holes front contact barrier height (φh) obtained with using p-a-SiOxCy:H layer, facilitates to a large amount of photogenerated holes to reach the interface of the front contact. It is also obtained that, the integration of p-a-SiOxCy:H double window layer i improves the short circuit-current density (JSC) which is causes by a good spectral response in the short wavelength. Consequently, an enhancement in the efficiency of the p-i-n single junction device was obtained and we could achieve the value of 10.7 %. This result makes the oxycarbide p-a-SiOxCy:H films which have wider band gap, lower absorption coefficient and good conductive properties more suitable for using as window and buffer layer in a-Si:H based solar cells.