Role of SiNx Barrier Layer on the Performances of Polyimide Ga2O3-doped ZnO p-i-n Hydrogenated Amorphous Silicon Thin Film Solar Cells

In this study, silicon nitride (SiNx) thin films were deposited on polyimide (PI) substrates as barrier layers by a plasma enhanced chemical vapor deposition (PECVD) system. The gallium-doped zinc oxide (GZO) thin films were deposited on PI and SiNx/PI substrates at room temperature (RT), 100 and 200 degrees C by radio frequency (RF) magnetron sputtering. The thicknesses of the GZO and SiNx thin films were controlled at around 160 +/- 12 nm and 150 +/- 10 nm, respectively. The optimal deposition parameters for the SiNx thin films were a working pressure of 800 x 10(-3) Torr, a deposition power of 20 W, a deposition temperature of 200 degrees C, and gas flowing rates of SiH4 = 20 sccm and NH3 = 210 sccm, respectively. For the GZO/PI and GZO-SiNx/PI structures we had found that the GZO thin films deposited at 100 and 200 degrees C had higher crystallinity, higher electron mobility, larger carrier concentration, smaller resistivity, and higher optical transmittance ratio. For that, the GZO thin films deposited at 100 and 200 degrees C on PI and SiNx/PI substrates with thickness of similar to 1000 nm were used to fabricate p-i-n hydrogenated amorphous silicon (a-Si) thin film solar cells. 0.5% HCl solution was used to etch the surfaces of the GZO/PI and GZO-SiNx/PI substrates. Finally, PECVD system was used to deposit a-Si thin film onto the etched surfaces of the GZO/PI and GZO-SiNx/PI substrates to fabricate alpha-Si thin film solar cells, and the solar cells' properties were also investigated. We had found that substrates to get the optimally solar cells' efficiency were 200 degrees C-deposited GZO-SiNx/PI.