Yen-Ho Chu

Crystalline silicon interface passivation improvement with a-Si1−xCx:H and its application in hetero-junction solar cells with intrinsic layer

Excellent passivation of an n-type Czochralski crystalline silicon surface is made possible by the deposition of hydrogenated silicon carbide (Si1−xCx:H) layers in the electron cyclotron resonance chemical vapor deposition. We investigate the structural effect with various CH4/SiH4 dilution ratios, and the lowest effective surface recombination velocity (21.03 cm/s) that can be obtained. We also demonstrate that the Voc can be improved more than 200 mV by inserting Si1−xCx:H layers to form hetero-junction with intrinsic thin layer (HIT) solar cells. The conversion efficiency of the planar HIT solar cell with μc-Si emitter can reach 13%.

Low Temperature (180°C) Growth of Smooth Surface Germanium Epilayers on Silicon Substrates Using Electron Cyclotron Resonance Chemical Vapor Deposition

This paper describes a new method to grow thin germanium (Ge) epilayers (40 nm) on c-Si substrates at a low growth temperature of 180°C using electron cyclotron resonance chemical vapor deposition (ECR-CVD) process. The full width at half maximum (FWHM) of the Ge (004) in X-ray diffraction pattern and the compressive stain in a Ge epilayer of 683 arcsec and 0.12% can be achieved. Moreover, the Ge/Si interface is observed by transmission electron microscopy to demonstrate the epitaxial growth of Ge on Si and the surface roughness is 0.342 nm. The thin-thickness and smooth surface of Ge epilayer grown on Si in this study is suitable to be a virtual substrate for developing the low cost and high efficiency III-V/Si tandem solar cells in our opinion. Furthermore, the low temperature process can not only decrease costs but can also reduce the restriction of high temperature processes on device manufacturing.

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%.