Microcrystalline Si:H solar cells fabricated using ECR plasma deposition

2003 ◽  
Vol 150 (4) ◽  
pp. 316 ◽  
Author(s):  
V.L. Dalal ◽  
J.H. Zhu ◽  
M. Welsh ◽  
M. Noack
Keyword(s):  
Solar Cells ◽  
Plasma Deposition ◽  
Ecr Plasma

Defect Densities, Diffusion Lengths and Device Physics in Nanocrystalline Si:H Solar Cells

2004 ◽  
Vol 808 ◽  
Author(s):  
Vikram L. Dalal ◽  
Puneet Sharma ◽  
David Staab ◽  
Max Noack ◽  
Keqin Han
Keyword(s):  
Solar Cells ◽  
Quantum Efficiency ◽  
Diffusion Length ◽  
Deep Level ◽  
Plasma Deposition ◽  
Solar Spectrum ◽  
Base Layer ◽  
Degree Of Crystallinity ◽  
High Hydrogen ◽  
Ecr Plasma

ABSTRACTWe report on the properties of nanocrystalline Si:H solar cells. The solar cells were of the p+nn+ type, with the n+ layer deposited first on a stainless steel substrates. The solar cells were prepared under high hydrogen dilution conditions using either ECR plasma deposition, or VHF diode plasma deposition processes. The deposition pressures were kept low, 5 mTorr in the ECR reactor and 50 mTorr in the VHF reactor. All the solar cells reported showed a high Raman ratio of crystalline to amorphous peaks. Properties such as dark current, deep level defects and shallow doping densities, and hole diffusion lengths were measured in these cells. It was found that the base layer was always n type, but that its doping could be changed by adding ppm levels of B during growth. A sufficient B doping even type converted the base layer to p type. It was found that there was a good one-to-one correlation between the shallow doping and deep level defects, suggesting that the same element, probably oxygen, is responsible for generating both shallow dopants and deep levels. The diffusion length of holes was measured in these cells using quantum efficiency vs. voltage techniques, and it was found that the diffusion length data could be explained very well by invoking trap-controlled recombination statistics. The dark I(V) curves could be represented by a standard diode model for highly crystalline materials, but as the degree of crystallinity was reduced, the diode factor increased. Voltage could be improved by reducing the crystallinity of the layer, but doing so resulted in a decrease in quantum efficiency in the infrared regions of the solar spectrum.

Microcrystalline (Si,Ge):H Solar Cells

2003 ◽  
Vol 762 ◽  
Author(s):  
Jianhua Zhu ◽  
Vikram L. Dalal
Keyword(s):  
Solar Cells ◽  
Buffer Layer ◽  
Quantum Efficiency ◽  
Fill Factor ◽  
Open Circuit Voltage ◽  
Defect Density ◽  
Cell Structure ◽  
Open Circuit ◽  
Base Layer ◽  
Ecr Plasma

AbstractWe report on the growth and properties of microcrystalline Si:H and (Si,Ge):H solar cells on stainless steel substrates. The solar cells were grown using a remote, low pressure ECR plasma system. In order to crystallize (Si,Ge), much higher hydrogen dilution (∼40:1) had to be used compared to the case for mc-Si:H, where a dilution of 10:1 was adequate for crystallization. The solar cell structure was of the p+nn+ type, with light entering the p+ layer. It was found that it was advantageous to use a thin a-Si:H buffer layer at the back of the cells in order to reduce shunt density and improve the performance of the cells. A graded gap buffer layer was used at the p+n interface so as to improve the open-circuit voltage and fill factor. The open circuit voltage and fill factor decreased as the Ge content increased. Quantum efficiency measurements indicated that the device was indeed microcrystalline and followed the absorption characteristics of crystalline ( Si,Ge). As the Ge content increased, quantum efficiency in the infrared increased. X-ray measurements of films indicated grain sizes of ∼ 10nm. EDAX measurements were used to measure the Ge content in the films and devices. Capacitance measurements at low frequencies ( ~100 Hz and 1 kHz) indicated that the base layer was indeed behaving as a crystalline material, with classical C(V) curves. The defect density varied between 1x1016 to 2x1017/cm3, with higher defects indicated as the Ge concentration increased.

Nanocrystalline Germanium and Germanium Carbide Films and Devices

2005 ◽  
Vol 862 ◽  
Author(s):  
Xuejun Niu ◽  
Jeremy Booher ◽  
Vikram L. Dalal
Keyword(s):  
Grain Size ◽  
Plasma Deposition ◽  
Open Circuit ◽  
Image Sensors ◽  
High Hydrogen ◽  
Strong Function ◽  
Germanium Carbide ◽  
Ecr Plasma ◽  
Hydrogen Dilution ◽  
Steel Substrates

AbstractNanocrystalline Ge and its alloys with C are potentially useful materials for solar cells, thin film transistors and image sensors. In this paper, we discuss the growth and properties of these materials using remote, low pressure ECR plasma deposition. The materials and devices were grown from mixtures of germane, methane and hydrogen. It was found that high hydrogen dilutions (>40:1) were needed to crystallize the films. Studies of x-ray spectra revealed that the grains were primarily <220> oriented. The grain size was a strong function of hydrogen dilution and growth temperature. Higher growth temperatures resulted in larger grain size. High hydrogen dilution tended to reduce grain size. These results can be explained by recognizing that excessive amounts of bonded H can inhibit the growth of <220> grain, which is the thermodynamically favorable direction for grain growth. Grain sizes as large as 80 nm were obtained in nc-Ge. Addition of C reduced the crystallinity. Mobility and carrier concentrations in nc-Ge were measured using Hall effect. Mobility values of ˜5cm2/V-sand carrier concentrations of ˜1x1016/cm3were obtained in larger grains. p+nn+ devices were fabricated on stainless steel substrates and compared with similar devices deposited in nc-Si:H. It was found that the voltage decreased and current increased in nc-Ge devices, in comparison with devices in nc-Si:H. Addition of C to Ge devices increased the open circuit voltage and shifted the quantum efficiency to larger photon energies, as expected.

Effect of Superlattice Doped Layers on the Performance of a-Si:H P-I-N Solar Cells

1986 ◽  
Vol 70 ◽  
Author(s):  
Rajeewa R. Arya ◽  
Anthony Catalano ◽  
James O'dowd
Keyword(s):  
Solar Cells ◽  
Gas Phase ◽  
Plasma Deposition ◽  
Activation Energies ◽  
Wide Bandgap ◽  
Narrow Bandgap ◽  
Optical Bandgaps ◽  
Superlattice Structures ◽  
The Individual ◽  
Conversion Efficiencies

ABSTRACTSuperlattice doped layers of the type ABABAB … have been prepared where A is the wide bandgap a-Si:C:H doped layer and B is the narrow bandgap a-Si:C:H or a-Si:H doped layer. The bandgaps of the individual layers were modulated by changing the gas phase composition of methane during the plasma deposition. By varying the structure of the films, superlattice p-layers with resistivities in the range of 106 - 107 ohm-cm with optical bandgaps of 2.0 - 2.4 eV, and activation energies of 0.35 - 0.48 eV and superlattice n-layers with resistivities in the range of 104 - 105 ohm-cm with optical bandgaps of 1.86 - 2.03 eV and activation energies of 0.38 - 0.47 eV have been obtained.P-I-N solar cells have been prepared with both p and n layers comprised of superlattice structures. Conversion efficiencies as high as 10.86% have been achieved under simulated AM1.5 Global conditions. Measurements reveal a marked improvement in both built-in voltage and carrier collection length.

Modified ECR Plasma Deposition

1993 ◽  
Vol 140-142 ◽  
pp. 79-88
Author(s):  
S. Nakamura ◽  
Toshikazu Akahori ◽  
Satoshi Nakayama
Keyword(s):  
Plasma Deposition ◽  
Ecr Plasma

Reactive plasma deposition of high quality single phase CuO thin films suitable for metal oxide solar cells

2017 ◽  
Vol 695 ◽  
pp. 3116-3123 ◽  
Author(s):  
Zhenzhen Li ◽  
Kemeng Tong ◽  
Ruifang Shi ◽  
Yonglong Shen ◽  
Yiqiang Zhang ◽  
...  
Keyword(s):  
Thin Films ◽  
Solar Cells ◽  
Metal Oxide ◽  
Single Phase ◽  
Plasma Deposition ◽  
High Quality ◽  
Reactive Plasma
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