Research on Nanocrystalline Silicon Film Solar Cells

2011 ◽  
Vol 347-353 ◽  
pp. 870-873
Author(s):  
Chun Rong Xue
Keyword(s):  
Grain Size ◽  
Solar Cells ◽  
Band Gap ◽  
Optical Band Gap ◽  
Volume Fraction ◽  
Silicon Film ◽  
Nanocrystalline Silicon ◽  
Processing Parameters ◽  
Crystalline Volume Fraction ◽  
Hydrogen Dilution

Nanocrystalline silicon film has become the research hit of today’ s P-V solar technology. It’s optical band gap was controlled through changing the grain size and crystalline volume fraction for the quanta dimension effect. The crystalline volume fraction in nc-Si:H is modulated by varying the hydrogen concentration in the silane plasma. Also, the crystallinity of the material increases with increasing hydrogen dilution ratio, the band tail energy width of the nc-Si:H concurrently decreases. Two sets of nc-Si:H solar cells were made with different layer thicknesss, their electronic and photonic bandgap, absorption coefficient, optical band gap, nanocrystalline grain size(D), and etc have been stuied. In addition, we discussed the relationship between the stress of nc-Si thin films and H2 ratio. At last nc-Si:H solar cells have been designed and prepared successfully in the optimized processing parameters.

Metastability in hydrogenated nanocrystalline silicon solar cells

2007 ◽  
Vol 22 (5) ◽  
pp. 1128-1137 ◽  
Author(s):  
Guozhen Yue ◽  
Baojie Yan ◽  
Gautam Ganguly ◽  
Jeffrey Yang ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Band Gap ◽  
Amorphous Phase ◽  
Reverse Bias ◽  
Volume Fraction ◽  
Nanocrystalline Silicon ◽  
Silicon Solar Cells ◽  
Single Junction ◽  
Hydrogen Dilution ◽  
Forward Current

Light-induced metastability in hydrogenated nanocrystalline silicon (nc-Si:H) single-junction solar cells was studied systematically. First, we observed no light-induced degradation when the photon energy was lower than the band gap of the amorphous phase; degradation occurred when the energy was higher than the band gap in the amorphous phase. The light-induced degradation could be annealed away at an elevated temperature. We concluded that the light-induced defect generation occurred mainly in the amorphous phase. Second, forward current injection did not degrade the nc-Si:H cell performance. However, a reverse bias during light soaking enhanced the degradation. Third, the nc-Si:H cells made with an optimized hydrogen dilution profile showed minimal degradation although these cells had a high amorphous volume fraction. This indicated that the amorphous volume fraction was not the only factor determining the degradation. Other factors also played important roles in the nc-Si:H stability.

Effect of RF or VHF Plasma on Nanocrystalline Silicon Thin Film Structure: Insight from OES and Langmuir Probe Measurements

2013 ◽  
Vol 1536 ◽  
pp. 161-166
Author(s):  
Lala Zhu ◽  
Ujjwal K Das ◽  
Steven S Hegedus ◽  
Robert W Birkmire
Keyword(s):  
Grain Size ◽  
Langmuir Probe ◽  
Volume Fraction ◽  
Nanocrystalline Silicon ◽  
Low Pressure ◽  
High Energy ◽  
Rf Plasma ◽  
Crystalline Volume Fraction ◽  
Langmuir Probe Measurements ◽  
Probe Measurements

ABSTRACTOptical emission spectroscopy (OES) and Langmuir Probe were used to characterize RF and VHF plasma properties under conditions leading to nanocrystalline silicon film deposition. Films deposited by RF plasma at low pressure (3 Torr), even with high crystalline volume fraction, show weak X-ray diffraction signals, suggesting small grain size, while RF films at higher pressure (8 Torr) and VHF films at both high and low pressure have larger grain sizes. The preferential growth orientation is controlled by the H2/SiH4 ratio with RF plasma, while the film deposited by VHF shows primarily (220) orientation independent of H-dilution ratio. Langmuir Probe measurements indicate that the high energy electron population is reduced by increasing pressure from 3 Torr to 8 Torr in RF plasma. Compared with RF plasma, the VHF plasma shows higher electron density and sheath potential, but lower average electron energy, which may be responsible for the larger grain size and crystal orientation. The growth rate and crystalline volume fraction of the film is correlated with OES intensity ratio of SiH* and Hα/SiH* for both RF and VHF plasmas.

Study of μс-Si:H Thin Films Prepared by RF-PECVD

2014 ◽  
Vol 492 ◽  
pp. 235-238
Author(s):  
Xiao Jing Wang
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Film Thickness ◽  
Optical Band Gap ◽  
Volume Fraction ◽  
Structure And Properties ◽  
Crystalline Volume Fraction ◽  
Microcrystalline Silicon ◽  
Silicon Thin Films ◽  
Transmittance Curve

μc-Si:H thin films have been deposited on the 7059 glass substrate by RF-PECVD. Effects of film thickness on structure and properties of Si thin films were investigated by XRDRamanUV-Vis and precision multimeter. Experimental results indicated that uniform dense microcrystalline silicon thin films can be prepared by rf-PECVD, silicon thin films transferred from a-Si:H to μc-Si:H along with film thickness increased. For μc-Si:H, XRD spectrum occurred (111)(220) and (331) peak, grain size and crystalline volume fraction increased with thickness enhanced, arrived at 82%; optical band gap of μc-Si:H is 2.0~2.36eV and decreased when thickness increased, the transmittance was added firstly and then reduced with film thickness increased, the transmittance curve occurred redshift;the photosensitivity of the thin films was improved firstly and then decreased with thickness increased, which was highest at 104 quantity in the transition zone from a-Si:H to μc-Si:H.

The dependence of the crystalline volume fraction on the crystallite size for hydrogenated nanocrystalline silicon based solar cells

2013 ◽  
Vol 1536 ◽  
pp. 113-118 ◽  
Author(s):  
K. J. Schmidt ◽  
Y. Lin ◽  
M. Beaudoin ◽  
G. Xia ◽  
S. K. O'Leary ◽  
...  
Keyword(s):  
Solar Cells ◽  
Volume Fraction ◽  
Crystalline Silicon ◽  
Nanocrystalline Silicon ◽  
Oxygen Impurity ◽  
Crystalline Volume Fraction ◽  
Three Samples ◽  
Crystallite Sizes ◽  
Silicon Based ◽  
The Impact

ABSTRACTWe have performed an analysis on three hydrogenated nanocrystalline silicon (nc-Si:H) based solar cells. In order to determine the impact that impurities play in shaping the material properties, the XRD and Raman spectra corresponding to all three samples were measured. The XRD results, which displayed a number of crystalline silicon-based peaks, were used in order to approximate the mean crystallite sizes through Scherrer's equation. Through a peak decomposition process, the Raman results were used to estimate the corresponding crystalline volume fraction. It was noted that small crystallite sizes appear to favor larger crystalline volume fractions. This dependence seems to be related to the oxygen impurity concentration level within the intrinsic nc-Si:H layers.

Fabrication of Undoped and N+ Microcrystalline si Films Using SiH2Ci2

1995 ◽  
Vol 377 ◽  
Author(s):  
Jae Seong Byun ◽  
Hong Bin Jeon ◽  
Jung Mok Jun ◽  
Jae Ho Yoo ◽  
Kyung Ha Lee ◽  
...  
Keyword(s):  
Band Gap ◽  
Room Temperature ◽  
Optical Band Gap ◽  
Volume Fraction ◽  
Crystalline Volume Fraction ◽  
Plasma Cvd ◽  
Conductivity Activation Energy ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Si Films

ABSTRACTWe have studied the growth of undoped and n+ μc-Si:H (:CI) films by Remote Plasma CVD using SiH4/SiH2Cl2/H2/He mixtures. It was found that the μc-Si film can be fabricated by increasing flow rate of SiH2Cl2 and/or H2. The deposited undoped μc-Si film exhibited a maximum crystalline volume fraction of 85 %, obtained from Raman spectroscopy. The n-type μc-Si film, deposited with SiH4/SiH2Cl2/H2/PH3/He mixtures, shows a room temperature conductivity of 2 S/cm, conductivity activation energy of 29.8 meV and optical band gap of-2.0 eV. The optical band gap of n-type μc-S1 deposited using SiH2Cl2 is much higher compared to conventional μc-Si film.

Metastability in Hydrogenated Nanocrystalline Silicon Solar Cells

2006 ◽  
Vol 910 ◽  
Author(s):  
Guozhen Yue ◽  
Baojie Yan ◽  
Gautam Ganguly ◽  
Jeffrey Yang ◽  
Subhendu Guha
Keyword(s):  
Solar Cells ◽  
Photon Energy ◽  
Volume Fraction ◽  
Forward Bias ◽  
Nanocrystalline Silicon ◽  
Material Structure ◽  
Light Spectra ◽  
Hydrogen Dilution ◽  
Carrier Recombination ◽  
Different Color

AbstractWe have recently reported that hydrogenated nanocrystalline silicon (nc-Si:H) solar cells exhibit metastability behavior that is significantly different from hydrogenated amorphous silicon (a-Si:H) solar cells. First, we studied the light-induced change of nc-Si:H cells under different light spectra, and observed that no light-induced degradation occurs when the photon energy is lower than the bandgap of a-Si:H, while light-induced degradation indeed occurs when the photon energy is higher than the bandgap of a-Si:H. Based on this observation, we conclude that the light-induced defect generation occurs mainly in the amorphous and/or grain boundary regions. Secondly, we found that forward-bias current injection in the dark does not cause any degradation in the performance of nc-Si:H cells, in contrast to observations in a-Si:H cells. This phenomenon can be explained by assuming transport percolation through crystallites, where excess carrier recombination does not cause degradation. Third, we found that a reverse electrical bias does not reduce, but rather enhances the light-induced degradation in the nc-Si:H cell performance. This enhancement increases with the magnitude of the reverse bias. We carried out a systematic study including measurements of quantum efficiency losses and fill factors under different color filters. In view of the heterogeneity of the material structure, we proposed a “back-to-back” diode model which explains most of the experimental results. Finally, we present results of the improvement of stability of nc-Si:H cells made using hydrogen dilution profiling. We find that the nc-Si:H cells with an optimized hydrogen dilution profile show very little light-induced degradation though these cells have a high amorphous volume fraction. This indicates that the amorphous volume fraction is not the only factor determining the degradation. Other factors, such as the structure and distribution of the amorphous phase, as well as the properties of the grain boundaries, apparently play important roles in the overall stability of nc-Si:H cells.

Light-Induced Effects on Fluorinated Amorphous and Microcrystalline Silicon Films

1996 ◽  
Vol 420 ◽  
Author(s):  
Hong-Seok Choi ◽  
Keun-Ho Jang ◽  
Jhun-Suk Yoo ◽  
Min-Koo Han
Keyword(s):  
Band Gap ◽  
Vapor Deposition ◽  
Optical Band Gap ◽  
Silicon Film ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Rf Plasma ◽  
Microcrystalline Silicon ◽  
Amorphous Silicon Film ◽  
Hydrogenated Amorphous

AbstractThe fluorinated amorphous and microcrystalline silicon (a,μc-Si:H;F) films have been prepared by rf plasma enhanced chemical vapor deposition (PECVD) with SiH 4 and SiF 4 gas mixtures. The stretching Si-O (1085 cm-1) and SiH2 (2100 cm-1) bands estimated from infrared (IR) spectroscope data have related to the evolution of crystallinity and the optical band gap was shifted by introducing Si-O bonds. The sub-band gap absorption coefficient in a,μc-Si:H;F films was about one order lower than that in hydrogenated amorphous silicon film (a-Si:H). The subband gap absorption in a-Si:H;F film was comparable to that in tic-Si:H;F films. The lightinduced degradation of a,μc-Si:H;F films were also suppressed.

Intrinsic and Doped m c-Si:H TFT Layers using 13.56 MHz PECVD at 250°C

2004 ◽  
Vol 808 ◽  
Author(s):  
Czang-Ho Lee ◽  
Denis Striakhilev ◽  
Arokia Nathan
Keyword(s):  
Performance Improvement ◽  
Volume Fraction ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Rf Power ◽  
Crystalline Volume Fraction ◽  
Microcrystalline Silicon ◽  
Bias Stress ◽  
Hydrogen Dilution ◽  
Low Threshold

ABSTRACTUndoped and n+ hydrogenated microcrystalline silicon (μc-Si:H) films for thin film transistors (TFTs) were deposited at a temperature of 250°C with 99 ∼ 99.6 % hydrogen dilution of silane by standard 13.56 MHz plasma enhanced chemical vapor deposition (PECVD). High crystallinity m c-Si:H films were achieved at 99.6 % hydrogen dilution and at low rf power. An undoped 80 nm thick m c-Si:H film showed a dark conductivity of the order of 10−7 S/cm, the photosensitivity of an order of 102, and a crystalline volume fraction of 80 %. However, a 60 nm thick n+ μc-Si:H film deposited using a seed layer showed a high dark conductivity of 35 S/cm and a crystalline volume fraction of 60 %. Using n+ μc-Si:H films as drain and source contact layers in a-Si:H TFTs provides substantial performance improvement over n+ a-Si:H contacts. Finally, fully μ c-Si:H TFTs incorporating intrinsic m c-Si:H films as channel layers and n+ μc-Si:H films as contact layers have been fabricated and characterized. These TFTs exhibit a low threshold voltage and a field effect mobility of 0.85 cm2/Vs, and are far more stable under gate bias stress than a-Si:H TFTs.

Analysis of Defects and Surface Roughness on the Hydrogenated Amorphous Silicon (a-Si:H) Intrinsic Thin Film for Solar Cells

2019 ◽  
Vol 966 ◽  
pp. 398-403
Author(s):  
Yoyok Cahyono ◽  
Novita Dwi Purnamasari ◽  
Mochamad Zainuri ◽  
Suminar Pratapa ◽  
Darminto
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Solar Cells ◽  
Band Gap ◽  
Indium Tin Oxide ◽  
Energy Band ◽  
Thin Layers ◽  
Oxide Glass ◽  
Energy Band Gap ◽  
Hydrogen Dilution

Effect of defect - through observation of energy absorption Urbach, on deposition rate, energy band gap, and surface roughness of intrinsic thin film are investigated using Radio Frequency Plasma Enhance Chemical Vapor Deposition (RF-PECVD). Films are grown on ITO (Indium Tin Oxide) glass substrate. Analysis of energy band gap is conducted to determine changes in the structure of a thin film of a-Si:H. Energy band gap is important to determine the portion of the spectrum of sunlight that is absorbed solar cells. From the characterization using UV-Vis spectrometer and the Tauc’s plot method, the width of the resulting energy band gap is greater if the hydrogen dilution is increased. It can be shown that the increase of the hydrogen dilution, will increase the energy band gap, and the surface roughness of thin layers. Instead, the improvement of the hydrogen dilution decrease the rate of deposition and Urbach energy. It is estimated that with greater hydrogen dilution, an intrinsic thin film of a-Si:H is more conductive for more reduction in residual of band tail defects or dangling bond defects.

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