Yu-Lin Hsieh

Investigation of intrinsic hydrogenated amorphous silicon (a-Si:H) thin films on textured silicon substrate with high quality passivation

In this study, the intrinsic hydrogenated amorphous silicon (a-Si:H) thin films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) was investigated for the application of the heterojunction silicon solar cell on the textured silicon substrate. During the process, we used the optical emission spectrometer (OES) and quadrupole mass spectrometry (QMS) to analyze the concentrations of free radicals in plasma. The results showed that the better surface recombination velocity (SRV) and passivation quality of a-Si:H thin films on the textured silicon substrate were obtained when the electrode distance at PECVD was 35mm. Furthermore, while the electrode distance was 35mm, the lowest electron temperature and the same spectrum ratio trend in OES (Si*/SiH*) and QMS (SiH2/SiH3) respectively were received.

Passivation quality and electrical characteristics for boron doped hydrogenated amorphous silicon film

Borons doped amorphous silicon (a-Si:H) that deposited on a n-type silicon substrate was prepared by plasma enhanced chemical vapor deposition (PECVD). The conductivity increases with increasing B2H6 flow when the electrode distance, working pressure and total flow rate are fixed. The Ellipsometer, Four Point Sheet Resistance Meter, Hall measurement, Secondary Ion Mass Spectrometer and Photo-conductance lifetime tester were used to obtain the electrical and physical properties of thin films. The research shows that while changing process parameters, the effect on the film that has the good conductivity and the carrier lifetime are most critical. When the amounts of the boron atoms increase, the conducting properties of the boron-doped hydrogenated amorphous silicon film increase effectively. However, too much boron atoms increase densities of the defects, thus reduce the carrier lifetime and affect the activation of boron atoms in films. Based on the results of the carrier lifetime ratio on intrinsic layer and stacked dopant layer, it is found that the carrier lifetime of the doping layer stacks over intrinsic layer can effectively improve the field effect on passivation film quality.

Doping profile control of epitaxial-like Si emitting layer for the application of c-Si solar cells

The formation of p-n junctions is a crucial step in the fabrication of photovoltaic devices. Standard processes such as high temperature (> 800 °C) diffusion cannot provide the shallow doped layers, with abrupt interfaces. In this study, the epitaxial-like boron-doped silicon (epi-Si) thin films as emitters of c-Si solar cells with structure of ITO/epi-Si(p+)/c-Si(n) are investigated under the modulation of deposited parameters, such as gas ratio, and working pressure. Applying the epi-Si:H (p+) shallow junction with abrupt interface leads to improve the short curent density (Jsc) of the planar c-Si solar cell is higher than 36 mA/cm2, and efficiency reaches above 15%.

The plasma diagnosis by optical emission spectroscopy for the study of phosphorus doped nanocrystalline silicone film growth

Phosphorus doped nanocrystalline silicon (nc-Si) that deposited on a p-type silicon substrate was prepared by standard radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD). The optical emission spectroscopy (OES) is used as a diagnostic tool for analyzing the processing species and intensity in plasma. The obtained SiH* spectra are recorded to explain results from the deposition rate of nanocrystalline silicon. The deposition rate increases with increasing power when the electrode distance, working pressure and total flow rate are fixed. Moreover, we also describe ratios of Hα* / SiH* and Si* / SiH* to represent the crystallization rate index and electron temperature respectively. Based on OES results, we can utilize plasma spectra as database to monitor film properties. The spectroscopic ellipsometer (SE) and hall measurements were used to further study the growth rate, crystallinity, and electrical property of the films. Under the process conditions of 225°C substrate temperature, 11mW/cm2 power density, 300mTorr working pressure and 30mm electrode distance, the best optimized n-type nc-Si films on a 4cm2 bifacial p-type Cz silicon wafer were obtained.

Investigation of a-SiOx:H films as passivation layer in heterojunction interface

In this study, the intrinsic hydrogenated amorphous silicon oxide (a-SiOx:H) thin films were prepared by Electron Cyclotron Resonance Chemical Vapor Deposition (ECR-CVD). High density plasma of ECR-CVD has many advantages: (1) faster deposition rate, (2) no electrode contamination, (3) low ion bombardment. The process parameters effect on a-SiOx:H thin films such as dilution ratio was investigated. In addition, this material will be applied to amorphous silicon / crystalline silicon heterojunction solar cells and improved the open-circuit voltage of solar cells.

Advances n-type nc-Si:H layers depositing on passivation layer applied to the back surface field prepared by RF-PECVD

In this paper, we optimized the process conditions that led to nanocrystalline silicon (nc-Si:H) growth of doped silicon films as a back surface field (BSF) layer in a symmetric cell structure were prepared by standard radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) in terms of the phosphorus flow (0~7840ppm) and substrate temperature (125-225°C) using a (PH3/SiH4/H2/Ar) mixture. High quality of BSF layer on surface passivation was obtained after enough pre-deposition time at low electron temperature. The life time up to 1.5ms and concentrations > 1019 in 4cm2 cells can be obtained. The plasma diagnostics related to nc-Si:H solar cell deposition process was performed simultaneously during the nc-Si:H solar cell deposition process using an optical emission spectrometer (OES) to observe the stability of the chamber condition. The spectroscopic ellipsometer (SE) and hall measurements were used to study their correlations with growth rate and microstructure of the film.

Investigation of a-Si:H films passivation quality by ECRCVD and application of silicon heterojunction solar cells

We investigated the quality of intrinsic layer by modulating the hydrogen dilution ratio (H2/SiH4) at various growth temperatures. The results of lifetime measurements indicate that a-Si:H intrinsic layer can successfully obtained the effective life time (~446us) and the implied open circuit voltage (~0.69 mV) under hydrogen dilution ratio (RH = 2) at 130°C even with high growth rate (>0.7 nm/s), that is good for industry production. The Voc increased about 28.3 and 32.2 mV with inserting a passivation layer (6 nm) on planar and texture c-Si wafer, respectively. Furthermore, with the addition of ITO as anti-reflection layer, we obtained that the conversion efficiency of texture HIT solar cell without back surface field (BSF) is 15.1% (active area = 0.783cm2) with Voc = 563 mV, Jsc = 36.7 mA, and FF = 73.1%.