Chao-Chun Wang

Optimization of Recombination Layer in the Tunnel Junction of Amorphous Silicon Thin-Film Tandem Solar Cells

The amorphous silicon/amorphous silicon (a-Si/a-Si) tandem solar cells have attracted much attention in recent years, due to the high efficiency and low manufacturing cost compared to the single-junction a-Si solar cells. In this paper, the tandem cells are fabricated by high-frequency plasma-enhanced chemical vapor deposition (HF-PECVD) at 27.1 MHz. The effects of the recombination layer and the i-layer thickness matching on the cell performance have been investigated. The results show that the tandem cell with a p

Fabrication of Flexible Amorphous-Si Thin-Film Solar Cells on a Parylene Template Using a Direct Separation Process

In this paper, we report on the fabrication of flexible amorphous-silicon (a-Si) thin-film solar cells on a parylene template carried by a glass plate without any adhesive. The a-Si thin-film solar cells could be separated directly from the glass carrier after a process temperature of up to 200°C. The a-Si and parylene films were deposited using high-frequency plasma-enhanced chemical vapor deposition and a parylene reactor. The parylene-coated glass plate was treated with thermal annealing and Ar, N2, or O2 plasma. Moreover, SiNx and/or SiOx films were used as barrier layers between the transparent conductive oxide and parylene films. Details of different gas plasmas and barrier effects were investigated in terms of surface morphologies and solar cell characteristics. The a-Si thin-film solar cell on a parylene template with an open-circuit voltage of 0.74 V, a short-circuit current density of 15.69 mA/cm2, a fill factor of 54.98%, and a conversion efficiency of 5.78 % could be obtained. After the 10-mm-radius bending test for 5000 times, the a-Si thin-film solar cells still exhibited a conversion efficiency of 4.94%. These results indicated that a-Si thin-film solar cells on parylene templates have high potential for flexible photovoltaic applications.

Power effect of ZnO:Al film as back reflector on the performance of thin-film solar cells

Aluminum-doped zinc oxide (AZO) is attracting interest as a potential transparent conducting oxide material for use in amorphous silicon (a-Si) thin-film solar cells. The absorption loss in the n-a-Si:H/Ag interface of the p-i-n thin film solar is high because the extinction coefficient of the Ag that is used as a back reflector is high. In this work, transparent conducting AZO films with a power in the range 500 W to 900 W prepared under Ar-ambient at a substrate temperature of 25 °C by RF-magnetron in-line sputtering. To minimize the absorption loss at longer wavelengths, an AZO layer we inserted at the n-a-Si:H/Ag interface of a solar cell with a glass/SnO2:F/p-a-SiC:H/buffer-layer/i-a-Si:H/n-a-Si:H/Ag structure and the performance of the cell with AZO/Ag deposited instead of Ag on the back contact, was investigated. The effects of the RF-magnetron sputtering deposition parameters on the optical, electrical and structural properties of the AZO films were analyzed. Optimized AZO films with high transmit...

Characterization of Nanocrystalline SiGe Thin Film Solar Cell with Double Graded-Dead Absorption Layer

The nanocrystalline silicon-germanium (nc-SiGe) thin films were deposited by high-frequency (27.12 MHz) plasma-enhanced chemical vapor deposition (HF-PECVD). The films were used in a silicon-based thin film solar cell with graded-dead absorption layer. The characterization of the nc-SiGe films are analyzed by scanning electron microscopy, UV-visible spectroscopy, and Fourier transform infrared absorption spectroscopy. The band gap of SiGe alloy can be adjusted between 0.8 and 1.7 eV by varying the gas ratio. For thin film solar cell application, using double graded-dead i-SiGe layers mainly leads to an increase in short-circuit current and therefore cell conversion efficiency. An initial conversion efficiency of 5.06% and the stabilized efficiency of 4.63% for an nc-SiGe solar cell were achieved.

Performance of a-SiGe:H Thin-Film Solar Cells on High-Heat Dissipation Flexible Ceramic Printable Circuit Board

In this paper, a flexible ceramic printable circuit board (FCPCB) consisting aluminum (Al) metal layer and ceramic layer is used as a substrate for solar cell fabrication. A 3-layer graded bandgap hydrogenated amorphous silicon-germanium absorber and an etched Al-doped zinc oxide are applied to single-junction cell fabrication to increase the cell conversion efficiency up to 6.3%. For temperature rise test, the heat energy could easily move from Al through the ceramic layer to the air. Both high-thermal conduction and thermal dissipation lead to a low rise in substrate temperature after long illumination, and thus to a high maintenance in solar cell performance. The bending test indicates a 12.6% degradation in conversion efficiency of FCPCB cells after bending 5000 times. The FCPCB substrate with high flexibility and thermal stability demonstrates great potential of use in flexible thin-film solar cell applications.

Properties of double-layered Ga-doped Al-zinc-oxide/titanium-doped indium–tin-oxide thin films prepared by dc magnetron sputtering applied for Si-based thin film solar cells

In this article, Ga-doped Al-zinc-oxide (GAZO)/titanium-doped indium–tin-oxide (ITIO) bi-layer films were deposited onto glass substrates by direct current (dc) magnetron sputtering. The bottom ITIO film, with a thickness of 200 nm, was sputtered onto the glass substrate. The ITIO film was post-annealed at 350 °C for 10-120 min as a seed layer. The effect of post-annealing conditions on the morphologies, electrical, and optical properties of ITIO films was investigated. A GAZO layer with a thickness of 1200 nm was continuously sputtered onto the ITIO bottom layer. The results show that the properties of the GAZO/ITIO films were strongly dependent on the post-annealed conditions. The spectral haze (Tdiffuse/Ttotal) of the GAZO/ITIO bi-layer films increases upon increasing the post-annealing time. The haze and resistivity of the GAZO/ITIO bi-layer films were improved with the post-annealed process. After optimizing the deposition and annealing parameters, the GAZO/ITIO bi-layer film has an average transmittance of 83.20% at the 400–800 nm wavelengths, a maximum haze of 16%, and the lowest resistivity of 1.04 × 10−3 Ω cm. Finally, the GAZO/ITIO bi-layer films, as a front electrode for silicon-based thin film solar cells, obtained a maximum efficiency of 7.10%. These encouraging experimental results have potential applications in GAZO/ITIO bi-layer film deposition by in-line sputtering without the wet-etching process and enable the production of highly efficient, low-cost thin film solar cells.In this article, Ga-doped Al-zinc-oxide (GAZO)/titanium-doped indium–tin-oxide (ITIO) bi-layer films were deposited onto glass substrates by direct current (dc) magnetron sputtering. The bottom ITIO film, with a thickness of 200 nm, was sputtered onto the glass substrate. The ITIO film was post-annealed at 350 °C for 10-120 min as a seed layer. The effect of post-annealing conditions on the morphologies, electrical, and optical properties of ITIO films was investigated. A GAZO layer with a thickness of 1200 nm was continuously sputtered onto the ITIO bottom layer. The results show that the properties of the GAZO/ITIO films were strongly dependent on the post-annealed conditions. The spectral haze (Tdiffuse/Ttotal) of the GAZO/ITIO bi-layer films increases upon increasing the post-annealing time. The haze and resistivity of the GAZO/ITIO bi-layer films were improved with the post-annealed process. After optimizing the deposition and annealing parameters, the GAZO/ITIO bi-layer film has an average transmitt...

Fabrication and chrarcterization silicon thin film solar cells deposited by HF-PECVD

The high frequency plasma enhanced chemical vapor deposition (HF-PECVD) is a well applicable deposition technique for large area and high rate deposition for silicon thin film solar cell application. This paper presents the properties of hydrogenated amorphous silicon (a-Si:H) films and high efficiency of p-i-n solar cells prepared using RF (27.1 MHz) excitation frequency. The influence of the power (10–40 W) and pressure (20–50 Pa) used during the deposition of absorber layers in p-i-n solar cells using pure silane on the properties of the films and solar cells are investigated. We summarize the power and pressure effect on properties and growth mechanism of a-Si:H films. It was found that the a-Si:H films prepared under various deposition conditions show widely various deposition rate, optical-electronic properties and microstructure. AZO films between two layers (n-layer and metal), the AZO back reflector was successfully implemented in a-Si:H singlejunction solar cells. After optimizing the deposition parameters, the amorphous silicon based thin film silicon solar cells with efficiency of 9.15 % have been fabricated by HF-PECVD. These are very encouraging results for future fabrication of high efficiency thin film solar cells using by HF-PECVD.