Abstract
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 °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 × 10−3 Torr, a deposition power of 20 W, a deposition temperature of 200 °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 °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 °C on PI and SiNx/PI substrates with thickness of ~000 nm were used to fabricate p-i-n hydrogenated amorphous silicon (α-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 α-Si thin film onto the etched surfaces of the GZO/PI and GZO-SiNx/PI substrates to fabricate α-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 °C-deposited GZO-SiNx/PI.
Highlights
Transparent conducting oxides (TCOs) are electrical conductive materials with a comparably low absorption of light
When the SiNx thin films are used as barrier layers between the gallium-doped zinc oxide (GZO) thin films and PI substrates, the refractive index of the SiNx thin films have to match that of the GZO thin films
For the GZO thin films, as their deposition temperature was raised from room temperature (RT) to 200 °C, the carrier mobility and carrier concentration increased and the resistivity decreased independently of the used substrates
Summary
Transparent conducting oxides (TCOs) are electrical conductive materials with a comparably low absorption of light. Araujo et al [12] added a disperse carbon interlayer between the n-α-Si:H layer and an aluminum zinc oxide (AZO) back contact They have found that an α-Si:H tandem solar with this structure could have a 10% increase in the short current density (Jsc) and a 20% increase in the efficiency compared to a standard solar cell. The deposited SiNx thin films have good properties and advantages as low temperature processed barrier layers, and they can be adopted in the thin film transistor (TFT) type ferroelectric random access memory (FRAM) These results prove that the additions of oxide buffer layers or barrier layers will improve the efficiencies of the fabricated thin film solar cells and FRAM. The surfaces of GZO/PI and GZO-SiNx/PI structures were etched by 0.5% HCl solution in order to increase the haze ratio, and the α-Si:H thin-film solar cells were fabricated on the etched GZO/PI and GZO-SiNx/PI structures, and their I–V properties were investigated
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